Phone interview?
I am currently studying in Rome for the semester, but I am also applying to SM internships for the summer. I already had one phone interview where they actually called me from the states. (Even if I didnt get the job, I guess it was nice to know they cared enough to make a really long distance call.)
So maybe just say that while you're working and are thus unable to come all the way out for a face to face interview, you would be happy to have a phone interview... or maybe an interview with a Webcam? Or maybe there is a theater conference somewhere near you where the theater may be going to interview people? Maybe you could meet at some mid point so you dont have to drive as far?
The other thing is that I think if they want to interview you, they'll work with you to have it happen one way or another. And theater work seems to be a contractual sort of work... I'm sure they wont think it's ODD that you're employed at one place and interviewing for your next job. And your intern experience makes you more valuable to them, in terms of experience, they want you bc it's on your resume... dont feel silly about saying what you do now and where you plan on getting to.
Eh, just my two cents... which is not worth as much in Euros. But good luck-- let us know how it goes!