Here's the list:
Heatran-Reversal Mountain
Rgi-trio & gigas- Underground ruins and twist mountain (both locations are close to each other)
Kyurem- Giant Chasm
Zekrom/Reshiram- Dragonspiral Tower (this one debatable)
These are all non-event legendaries that are in caves. So, none of the caves listed hold and type of legendary Pokemon in BW2. Source
