During an episode of Rush back in the 1990's he explained that the 'phone lines' aren't really 'lines' but something else.  I forget what the terminology is, so if any of you know what they are please tell.

I was listening to an U.S. talk show recently and the host said they can hold (up to) 17 callers at once.
It seems the max for WBZ-AM and CFMJ is four.