You can get one on one save and one on the other, however I don't believe you can combine your efforts on both saves. For example on Hotfoot, I don't think you can travel 20 kilometers on one save and 5 on another and get the trophy, but you can do hotfoot on one save and ac/dc on another.
hew hints....for ac/dc it takes AGES so when you go underground and are about to link the electrictity thingy, start extracting electricity and then turn off the controller....he will be locked into extracting the electricity and come back after like 15 mins and viola...because i never got it on either of my 2 playthroughs. oh, and with the kill 25 guys while on a moving train, do this on the early mission, otherwise its very very hard. i played through 3 times, the last time to methodically get EVERY freakin blast shard haha. good luck :) any your stuck on message me