"Subway alumni" was a popular term when Notre Dame's football team played in New York City, but it is not used today.
22 January 1933, Charleston (WV) Daily Mail, pg. 8:
NEW YORK, Jan. 21 (UP). - New York City's "subway alumni," those thousands of men and women who never set foot on a college campus but who, nevertheless, take their football as seriously as any "rah rah" boy, will have an imposing list of games from which to choose in 1933.
2 December 1933, Lincoln (NE) Star, pg. 8:
NEW YORK, Dec. 2 - (INS) -
(...)
"Subway" Alumni.
So up today from the sidewalks of New York will come the famous "Subway Alumni" to rally around its favorite team and try to make it win.
16 November 1935, Chicago Daily Tribune, pg. 23:
The subway alumni of Notre Dame will have their homecoming at Yankee stadium tomorrow.
12 November 1936, Washington Post, pg. X19:
Army's Game
With Irish
A Sell-out
Notre Dame's "Subway
Alumni" Make Fray
Box-Office Success.