The TRANZAC has a variety of things -
Flying Cloud Folk Club (which I'm involved with) are on Sundays September after labour Day to the end of May (Easter, Xmas/New Year, sometimes Thanksgiving excepted) These are concerts and not jams.
Comhaltas have sessions twice a month - 2nd and 4th Wednesdays, except summer.
There have been open stages and a Saturday series organised by Norm Hacking weekly.
Wednesday's have had music, weekly in the style of Django Reinhardt (might have spelled that wrong - sorry) and I believe they have had an open jam on Monday's.
Note: the TRANZAC has a Main Hall (Cloud), the "Tiki Room" (sessions), and the Southern Cross.
As for 'grass, which was the direct question, I have to say not really. Phone number there is 416 923 8137. And before I'm flamed for advertising, I have no finacial stake there - people doing the above, (mostly) do it for the love of the music and volunteer - as do other places such as Acoustic Harvest. A large problem in Toronto is getting the word out - once your in the know it is easy to find out, however, getting the word out - apart from community radio is an excercise in persistance. By the way I might as well plug ASteve Pritchard's Old Time/blue grass show - radio boogie on CKLN (10 pm Wednesday's) which compliments other shows on CKLN and of course CIUT as you all know.
Rana