For the sake of discussion, I am presuming that each round-trip requires one pair of equipment and then removing "redundant" round-trips (e.g. Ottawa-Montreal/Montreal-Quebec with an Ottawa-Quebec round-trip). I'm also ignoring weekends and "just" going with Monday-Friday trains and sticking with adding up eastbound trains. Here's what I have:
Montreal-Quebec:
-5x daily trains (#20, #22, #24, #26, #28)
--2x daily (#22 and #24) originate Fallowfield/Ottawa
--2x daily (#26 and #28) originate Ottawa
Ottawa-Montreal:
-6x daily trains (#22, #24, #34, #26, #28, #38)
--2x daily (#22 and #24) originate Fallowfield/Ottawa, terminate Quebec
--2x daily (#26 and #28) originate Ottawa, terminate Quebec
--2x daily (#34 and #38) originate Ottawa, terminate Montreal
Toronto-Ottawa:
-10x daily trains (#50, #52, #40, #42, #644, #44, #46, #646, #54, #48)
--None appear to run through to Montreal
Toronto-Montreal:
-6x daily trains (#60, #62, #64, #66, #68, #668, #650)
--None appear to run through to Montreal
Up here we thus seem to have 23 sets required. On the other parts of the Corridor, Toronto-Sarnia requires two sets (85 turns as 88 in London, while 84 turns as 87 in Toronto). Toronto-Windsor requires five sets (one turns in London).
So that's 30 sets (on what I suspect are unfavorable assumptions). Two more sets would provide maintenance/bad order coverage...so this is probably a break-even proposition. It might represent a small gain (I'm having to make certain assumptions) or a small loss (depending on seat capacity...I've seen a few trains with six or seven cars on occasion).