I'm the keyboard half of a "Covers" Duo. Dual vocals, Keys, Drums.

For modern uptempo stuff using midi files, drummer locks in no problem because some years ago he had to learn to play ballroom "fixed tempo" music at EXACTLY the right speed (initially by using a metronome) so playing at a specific speed and not changing tempo is now second nature.

I agree that drummers left to their own devices can be variable in tempo, but lets not forget that before styles and midi files the drummer / bass / rhythm set the tempo and its a bit of a culture shock to have to maintain tempo against an external reference!

In summary: You need a good drummer and excellent discipline but it's not impossible.