They shouldn't be using one codec, they should be using one edit solution. What they should NOT be doing is working on the same project with two different editing applications. They do not mix well. YOu will not be able to share cuts and media without expensive software (Automatic Duck) and a lot of effort, and I mean a LOT of effort. Too much to make it workable.
Choose one edit system and make both editors use that. If they only know one and not the other, then choose one NLE, and hire editors that know how to use it, or the odd man out learn the other one.