I think it was the patch that they released introducing the "Endor on fire" free map that had support for full bot support on the "Walker Assault" game mode. It might have only been that map when the patch came out, but I think was eventually extended to all of the big 40-man PvP maps.
The "Challenge" stuff I remember, that was on launch, as was just the small infantry-only maps. When they supported the 40-man maps it was with full vehicle support. Getting into an AT-AT and blasting through one of those maps was kinda fun.
Regardless, we've already played the bot support (full teams of AI) in SWBF2 in the beta a month ago. And we've only had a taste, looks like there are going to be several bot modes on launch, possibly more added for free later.