AMENDMENT: Apologies to Cliff, you can be assigned Gateway travel from home to somewhere besides your crew base BUT the rules are different, which is the point I wanted to make. You can't report for duty at the other location any earlier than if you had been put on an actual DH from base and received rest (if required). On the 767 based in JFK, I never had to leave home prior to my trip beginning in AIMS, and it was never taxed, whereas I was taxed for anything that touched JFK.

Source: CBAG page 13

Thanks to Galaxydriver for challenging me on this. Expeditious travel and 20-hour rules still apply.