I understand the "subway to nowhere" argument but I'd still add some caveats:
-VMC was designated as a provincial growth centre and had long been eyed as such so it's really not like they just drove the subway up to some random field and then figured out what to do. Yes, there isn't much there now but there is actually a larger plan going on.
-Meh, maybe an LRT would have been just fine but I'm not sure the economy of scale is there once you're already building the darned subway. One advantage of LRT (contrary to what the Fords think) is you get a presence on the street that encourages development etc. but that wasn't going to happen on Jane Street. The idea was to hook up to the node at the 407 (when the t-way is built!) and to foster transit-oriented-development in Vaughan. At worst, they're laudable goals and while I understand how it could have fuelled Scarborough's "me too!" neediness, I'll eat my hat if any councillor mentioned the word's "Transit-oriented-development" during that abominable debate.
-As for "Bang for the buck," York Region got another $1.4B for Viva so they're really doing OK. The only place they got stiffed was the Yonge line and $1B wouldn't have been enough to make a difference there.
Perfect, it ain't. And personally, I think Vaughan could have been more agressive with its density targets, but I still think calling it a "terrible precedent" is an unfair stretch. There's more than enough Stupid in Toronto for the city to wear the Scarborough mess-up on its own, without blaming other municipalities successfully working within a larger planning framework.