Hi Elizabeth.
you somehow needed a mac (or pc) in the studio.... You would record your piano with pianoteq4 as a plugin inside Logic at home - and take the whole logic song with you to load it into the mac at the studio and refine and mix with the rest.
In case the studio had a PC instead of a mac, you would, like you said, save the midi file and also keep in mind which preset you used or what you changed at a preset, and then load the midi file there, in whichever program the studio machine had.
Surely the studio has some mac/PC?
Only thing is you needed pianoteq installed at that studio-machine too, of course, if you want to further work on the midi file with pianoteq.
Best and easiest would be to have, in your case, Logic at home and in the studio, as you could work on the whole song or whatever you play at both places. But like said - that is not strictly necessary.
In case pianoteq is not installed at this studio....
Pianoteq requires "challenge response", a copy protection I am not particularly fond of but which is said to lead to lesser "thiefs". (I doubt it, but that's another story, and well, the developers decide).
So pianoteq has to be activated at home on your mac - and in the studio. I have no clue who runs the studio, of course, so best would be they had a licensed copy of pianoteq also, which, I tend to think, every studio would benefit from^^.
So you can take audio and midi files with you, whole songs made in Logic or where-ever, but not so simple a plugin like pianoteq. That's why, off topic a bit, I most of the times buy software which gets me serial numbers or something like that. As honest customer I could just go to 3 studios, for example, until I like one. I would install my software there - and uninstall it after I am ready (as to leave it to them would make them "crack studio and companies" ;-)). A serial can be installed as often as we want, just "on the machine I work on right now" plus my home-machine...
Has the studio a mac, PC, and could you persuade them to buy Pianoteq, that's maybe the question^^.
Surely others will chime in and help with solutions I can't see this minute^^.