Neither the current federal government nor the province really want it.  They are stuck with it because of previous political mis-steps.  It is difficult to walk away.
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If the vote were taken now, neither the feds nor the province would authorize this nonsense.
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Harper put up the $600m, roughly the GST on the project.  It was contingent on the city and the province putting much bigger shares into the kitty - money the feds knew they didn't have, and couldn't easily raise.  It was political mischief designed to cause the most trouble, not to build transit.
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Finally, the reason the Conservatives don't oppose it is because (a) it doesn't improve transit;  (b) it robs more worthwhile projects of funding; (c) it funnels construction money to Conservative supporters; and (d) it functions principally as a subsidy to a failing mall that was built in the wrong place 45 years ago.  It would only be "government waste" if the money wasn't benefitting Conservative supporters.