Ben’s closed in ~2006. Near as I can tell from the Googles, it might have been torn down “Demolition on Ben’s Deli began in September and was completed by November 2008“.
Looking around using street view confirms (these are all ~2023):
Ben’s was here, 990 Blvd. de Maisonneuve W. 
…across Metcalf St. street… 
…kiddy-corner… 
… and across Blvd. de Maisonneuve.
Not quite the massive skyscrapers I remember. I was smaller then?
My first visit was ~1985 (I was in the army, had a long wait for bus to Toronto, so I went).
Ben’s was much larger than Schwartz’s. Easily 2x the counter space and ~20 4-tops, maybe more:
Yes, Ben’s was this ugly. Luckily the food was a great distraction. 
Schwartz’s is still open, at least as of 2023-04.
and we know it’s good, ’cause pretty sure last time we were in Montreal, we went to Schwartz’s, not Ben’s. The last time I was at Ben’s was when I was coming home from Trois Rivière, rushing back to join Joan at the Holiday Inn in Ptbo for our 10th anniversary (so ~2000-04-28); she said I either arrive by 6pm or she’d pick someone else to celebrate our 10th. I go there with time to spare, big jar of pickles, a few lbs of meat, and a couple loaves of the rye bread they use.
Same stuff, but you gotta be willing to sit with strangers if you want to eat inside; it’s either sit in an open chair at the counter, or at the tables to the left; no such thing as a reserve seat.
At least you can order takeout from the next door window:
And if we can’t do Schwartz’s, there are many others…
