The "numbers just don't add up" for the Ontario Progressive Conservative's plan to take on the capital costs of running and expanding Toronto's subway network, a prominent public transit advocate said Sunday.

In their election platform revealed this weekend, the Ontario PCs committed to upload costs for maintaining and growing the subway system, and promised $5 billion in new funding for several major subway projects: the Scarborough extension, a proposed Sheppard extension, a downtown relief line and a Line 1 extension to Richmond Hill.

"It is time for the provincial government to stop making excuses and do what is necessary to get shovels in the ground and get subways built," the platform, called People's Guarantee, reads.

The biggest chunk of the $5 billion will go toward taking on the city's $1-billion stake in the Scarborough subway extension, as well as covering the expected cost overruns of the now $3.3 billion project.

"This is $5 billion in new money for the TTC. This is a significant investment in Toronto subway infrastructure that has been long neglected by the Wynne Liberals," Ontario PC Leader Patrick Brown said in a statement provided to CBC Toronto.

'Creative accounting'

Transit advocate Steven Munro, author of a municipal affairs blog, says the proposed funding is not nearly enough given the need for regional transit upgrades and the potential total costs for all three undertakings the PC's have marked for development.

"Any one of those could eat the entire $5B and more, just on its own," Munro told CBC Toronto.

In the platform document, the PC's say significant financial support from Ottawa will be necessary for the projects to come to fruition.

"It is my hope that the Federal Government will match this funding which would help this landmark investment go even further," Brown said.

Munro, however, was similarly critical of the PC's proposal to "upload" costs of maintaining and expanding subway infrastructure to the province (trains, tracks, tunnels and stations), calling it "creative accounting" meant ultimately to minimize a PC government's deficit figures. The move would mean additional costs for Queen's Park while Toronto gets to hang on to revenue generated from fares.

It's not an entirely new idea, but previous PC leaders have failed to garner enough support outside of the GTA to make it politically feasible. As Toronto's subway system becomes an increasingly regional asset, though, it may become more palatable to voters elsewhere in Ontario.

"This is the really mysterious part to me. I think they have underestimated the true cost of owning the subway, particularly given that they say they're going to leave fare revenue with Toronto," said Munro, adding that it's a "myth" that subway systems generate money over the long-term.

While the PC platform allows for a small deficit in the first year of government, it claims the province will run a surplus each year after until 2022.

"These are big goals," Brown acknowledged during a Mississauga Ont., news conference on Sunday, adding said he's standing by them.

"I can tell you our platform is fully costed, it's affordable," saying at least two senior economists in Canada have looked at and approved of the platform's numbers.

"This is something important to me, the gridblock in the GTA is suffocating," Brown said. "We going to make sure that the existing infrastructure promised by the government actually get expedited."

Mayor Tory reviewing proposal

"The idea that the province can upload the costs of the subway and still be ahead of the game — the numbers just don't add up," Munro argues.

In a statement, Toronto Mayor John Tory reiterated his stance that "all provincial parties must recognize Toronto's unique needs as Ontario's biggest city and economic engine."

Tory has previously criticized Premier Kathleen Wynne and her Liberal government for its apparent reluctance to contribute funding to major, regional transit projects. For example, Queen's Park put up $150-million to study the downtown relief line but has said repeatedly it is too early to commit money.

"Clear support for Mayor Tory's relief line and the Scarborough Subway Extension is welcome," the mayor's spokesperson said.

"The Mayor will be reviewing this proposal — as he will be reviewing all parties' platforms — and he looks forward to meeting with Patrick Brown to discuss it further."

Munro points out that even though the PC plan may be attractive to Torontonians fed up with inadequate transit, it focuses exclusively on the city's subway projects and a select few light rail projects outside of the GTA that are already under construction.

A big gap, he argues, is in inter-city and regional bus route in areas the province that have seen a reduction in service by private companies like Greyhound. Furthermore, many of Brown's commitments could never come to fruition within a single term, meaning promises may never materialize.

"The construction projects alone are multi-term projects," Munro said.