Agreed. I thought this was a very clever political move. Defeating Ford is the primary objective, of course, but defeating Stintz is also useful, since she's a nuisance candidate who only serves to siphon away votes from stronger, anti-Ford candidates.
Axing the Scarborough subway is riskier than, say, axing a 905 transit project because Scarberians are more attached to transit, but I still think it's a useful tactic because (1) you can get elected even without any support in Scarborough (Scarborough is not an election killer, like losing Ontario federally); (2) The optics of subway really change once people are confronted with the fact that you can't have it without a major tax hike, and, (3) most of the people who would vote for Ford in Scarborough care more about taxes than subways, anyway.