Dan has some good points there.
On top of that though, if you already have files saved in "native" format, then all you need to do is to send the programs back into the machine. Then when downloading them from the machine, just use the tape I/O to save. Now its in the 3-digit format. Its worked on everything I've run so far from M(T)32, M(T)plus, and Fusion. Its possible (like Dan said earlier) that the older controls won't output thru Tape. So I'm thinking this might be the case with the earliest versions of M32 and older (M1 and M2).
Used to use Griffo software years ago but got away from it (No real reason, Griffo is good stuff). So any programs we had still in native format, after it was loaded and ran, we just saved it as an NC file thru the Tape I/O. Mazatrol is way too easy to use and program to have to justify "offline" programming for us (and many other places I've worked at). Especially on lathes since you can probably program a dozen parts at the machine while you're running one. I don't care for Mazatrol on the mill so we don't use it there.
The test is simple. Just have them output the Mazatrol programs thru Tape I/O (be sure the settings are correct) and see what you get. If you get something that looks like a bunch of macro routines with 3 digit g-codes, it should be fine. Then to test that, just upload this program back into the control and see if the Mazatrol program looks correct.