Well, while most of the original cast of A Chorus Line was not well-known to the general public, most had been featured dancers in shows for years and were known to the real theatre fans. Had there been a BWW back in 1975, several posters would have recognized the names Priscilla Lopez, Baayork Lee, Carole (later Kelly) Bishop, and Robert Lupone.
And Donna McKechnie was very well known at the time. She wasn't quite famous, but she been featured in a couple of major shows (COMPANY, PROMISES PROMISES) and had been chosen along with Gwen Verdon, Helen Gallagher and Paula Kelly to open the 1973 Tony Awards as one of the elite triple threats on Broadway.
So, it wouldn't be out of character for Avian etc ... to cast someone with something of a "name" to play Cassie and, given they're going to be looking mostly at veteran chorus people, I certainly imagine that many of us here will recognize several of the performers they cast in the other roles.
"What a story........ everything but the bloodhounds snappin' at her rear end." -- Birdie
[http://margochanning.broadwayworld.com/]
"The Devil Be Hittin' Me" -- Whitney