Sigh...
Seriously, If I hear the arguement that you have to be able to sing High C's to play tenor roles on Broadway, I will scream.
VERY rarely is there any role that you have to consistantly sing High C's. I can only think of a few roles that actually need you to sing a High C - that being Judas in JCS, Beadle Bamford in Sweeney Todd, and Pirelli in Sweeney.
Most Tenor roles require you to sing up to either a High A or a High B at the extreme...but the most common high notes are around High A or Bb.
You are so right to distinguish the requiements for singing for Musical Theatre and Opera. High C's are more common in Operatic Tenor roles, but even, then is not as EXTREMELY common, as you think.
Furthermore, it would be great to be able to sing a solid High C, as a tenor, but there are different categories of tenors in the operatic classifications too, that have various range requirements....so the point of being able to sing High C's to be a true-blue tenor is ridiculous.
That is all.
Cheers,
The Balladeer
"Someone tell the story...Someone sing the song...."