Hi, I have done several musicals throughout about 3 decades (with just flute and picc. and I'd say that finding one with just a flute/picc book is very rare. The ones that I've done always had other reeds in that book. That is not to say that an enterprising flutist can't find something to play during the gig if they're willing to write it out.
One can browse the list here as it shows the instrumentation of many musicals.
http://www.mtishows.com/
~Bilbo
N.E. Ohio