Not exactly flush -- but with less gap than when using standard CZ mags. I stepped away to take a photo: there is a gap, but nothing that can't be tolerated or dealt with by adding a different base. Is it worth the time and effort? For the 15-round mag, and about the same as when using CZ "compact" mags, perhaps.
I haven't tried the 18-round mags (have only seen them in catalogs), but they have a thicker base -- which is probably added to increase the length a little (for extra capacity.) The extra thickness won't fill the gap, but will likely extend the other way... I didn't know the 18-rounders even existed until yesterday. I see no reason why they wouldn't work.
I'll bet that CZ-40B mag bases, if they're available from CZ-USA, can be modified to fit the base perfectly. They're thicker than standard bases (but fit on standard mags) and fill a gap that is similar to that seen with the P07.
Just an update. I tried the CZ 75 mag followers in the MecGar 228 mags and they worked fine. Due the length of follower you can only get 13 rounds in the mag.