I don't think Forbes takes things like ML Square and the other physical holdings into account (arena, mastercard centre, condos) etc.... but I don't think they do that in Montreal either (Bell Centre, Tour des Canadiens which is under construction, practice rink in Brossard, etc...) I think its just the team that is valued in both cases.
That said, they are just guesstimates, and I've long had issue with these forbes articles because they don't have access to the real books, and they are just fun little article the magazine does where they put some financial guys on this for a couple weeks, make some guesstimates and mvoe on to doing what they normally do. Everyone pretends they are experts, but actual sale prices and Forbes Guesstimates have never really lined up in any year that teams were sold.