If in a "tent city" field conditions should/will be in place so it no doubt it will fall to 3MCS to feed them/provide packed lunches etc so not too bad there (I've had 1st hand experience recently and it was very good grub), also would/should be entitled to LSA if unable to return to home unit on days off due to service need (No different to being on Salsbury plain/exercise). So that should help cover the extra costs a little bit.
Note I used the word "Should" a lot, the reality might be something completely different to save money.