Houston crews also fly to and from IAH, and have quite a few of the overnights there (nice for the guys that live on the north side of town close to IAH). But it works exactly like every other non-domicile city works; you're never required to show at IAH. That would be a little rough on the commuters.
Besides, there are few enough flights to/from IAH that it doesn't involve all that many crews. I suppose with irregular ops they might consider putting a HOU reserve into a taxi to fill a slot at IAH (say, if somebody there on a overnight got sick), but it isn't a common occurrance.
Snoopy