no, it boosts the faction of your guild (and alliance). That, in turn, can eventually give you control of outposts and cities, giving you access to reserved areas, but I think it may be awhile until we get that far. :p
My guild (of one) now has 20k faction, which isn't bad compared to Zoo's 5k (cough). And yea, you can only control your little gorup of 4...the other 2 groups of 4 are kinda random. Still, I bet if you time it via TS and enter mission at the same time, you'll probably have a good chance of making it into the same mission.
Anyway, it's fun, but i've only done it with my A/R so far...first as a bleed barrager w/interrupts and more lately as a degen ranger with interrupts. Bleed + poison + seeping wound is some pretty mad degen...pin em down and interrupt em too and I can thoroughly pwn guys.
Anyway, I may post my build eventally. You should come A/B with us.