What to do to my party?

Hey Planescape Experts,

I'm a first time poster and I'm here because I'm running my Paragon Tier D&D Game in Sigil for the first time, and I have a question about what y'all think should happen.

Background: First, my strategy for this campaign has been to gather up information from the 4e books and form the old 2nd ed books, merge them in ways I like and make a fair amount of changes to make it my own. I don't love the 4th ed material, so I've ended up using a lot of the old planescape material to populate the world (We're running 4th edition primarily because these are all people relatively new to D&D - most of them started in a heroic campaign that I ran about a year and a half ago - and they were all more excited about the newest stuff then the old editions). So in my version of Sigil here are the relevant changes:

After the Faction War, Shemeshka leads a new organization - the Merchant's Guild - that is the typical oppressive overbearing badguy organization in the game. They have great wealth, and therefore power. One of the things they've done is erect City 'Docks' - a series of 20 large portals to other planes. They use these docks to import goods, and allow others to import goods through them with the payment of a very heavy tax. They have bribed members of various powerful organizations, and are responsible for much of the order in the Cage.

This organization has left Estevan and Zadara out on their butts with little to show for it. They've therefore teamed up and are running the Planar Trade Consortium, now a small upstart looking for new hidden portals to undercut the Merchant's Guild, and find other ways to cut into the MG's control of the economy. The Party has been hired by the PTC as independent contractors to do a variety of tasks. This won't be the primary overarching plot for the campaign, but we've played approximately 5 sessions with all the focus being on their work for the PTC.

I'm planning on running an updated version of Doors to the Unknown soon, and I wanted to introduce the Society of Locked Doors earlier in the game. In my version of Doors to the Unknown, the SLD is going to be a bit more powerful then they are depicted in DttU. Naturally, the SLD hates these docks, and one day as the party is passing nearby, they hear screams. SLD members have lit the 'docks' on fire in a suicide-style bombing and they're fighting the Merchant's Guild. The Party arrives on the scene seeing 40 Merchant's Guild Guards (who they've typically fought before in groups of roughly 5 or so) fighting 5 remaining SLD members. Now at this point, the party hasn't heard of the SLD and doesn't really know why this group is fighting the MG. But, I guess apparently on the view that the enemy of my enemy is my friend, and seeing an opportunity to kill some MGers, the party attacks these 40 MG members. I was not at all expecting this and was setting this up mainly as an introduction to the SLD and thinking of a cool skill based encounter where the party attempts to put out the fires. This attack is super dumb for a variety of reasons:

1. There are 40 of them. There are 7 in my party (its a big group and everyone made it this night). I repeat - there are 40 of them.
2. They've been told previous by Estevan not to fight with the MG directly and out in the open - exactly what they're doing here - because he doesn't want to arise their ire too much, because at this point the MG is still vastly more powerful than the PTC.
3. While they're all Clueless, they've gathered so far who the Lady of Pain is, and they know that while she doesn't interfere with much, she doesn't like her portals being messed with.

So basically where I'm at is this: The Party has killed off approximately 10 of the 40 members, but they're starting to wear down. Its clear that they wouldn't be able to kill all 40 (though they don't seem to be so sure), but they are considering retreating shortly. However, now they see Dabus hovering down the road behind them. The other areas of the docks that they're not fighting in have fires that are being put out, but in there area the fires are spreading because the MG are busy fighting with the Party instead of people working on putting out the fires. The Party, seeing the Dabus, are shouting and trying to make it seem like the MG have burned down their own portals or that they started the fight with the party - both extremely implausible lies with associated poor bluff checks. This is where we broke after last night's session.

So I'm trying to decide what makes sense to happen here, and what the Dabus would do when they arrive: I understand that Dabus generally don't fight, but most of the background I've read does suggest that they will when they think they need to and that this includes stopping riots or other chaotic problems. So I'm trying to decide whether the Dabus fight with the Party, try to fight with the Party and the MG in order to break the fight up so that they can repair the 'docks' and put out the fires, or just ignores them both (seems unlikely). In their weakened state, the Dabus could pretty easily take care of them. I know that if the party does escape with their lives, they'll now be in BIG trouble with the MG, who will stop at little to find and stop them. The other thought is that while they didn't start this chaotic fire, they definitely perpetuated the problem by jumping in on the fight - does it make sense for one or more of them to be Mazed? Also, while this is pretty clearly a big 'newsworthy' type fight, it still seems too small to get the Lady herself involved.

Basically I'm hoping for some clearer explanation of what it makes sense for Dabus to do in this situation, and how any other entities/organizations/power relationships might be affected by this very surprising (and dumb) move by my party. Thanks for your help - it is much appreciated.