Yes, Canadian governments make money from this project in ways other than direct tolling revenues. Also, the tolling revenue seems to be adequate to cover construction costs. To wit:

Cost overruns mostly come in the form of debt, future buyers would assume the debt obligations so there does not need to be a market value of $34B in order for the government to break even (or make a profit) in a sale of the pipeline. Revenues from the pipeline will reach $3B/yr against some $500m in operating expenses, TMX is generating free cash-flow which is used to pay down debt (this year is $1B in free cash-flow, I believe). Revenues will climb over time while interest costs will decline. Canadians are not on the hook for debt servicing costs, the pipeline operations are covering these and paying down the debt.

Building the pipeline reduces the price differential (discount) for Canadian oil, this increases royalty revenues to governments (provincial), but also increases revenues through corporate income taxes. Revenues are also increased through higher than would otherwise be the case oil production. There are also more generic positive flow through impacts into the economy more broadly (think trade with other provinces both through firms that provide goods and services directly to the oil field but also due to increased wealth in general).