Your analysis seems quite coherent.
On the one hand, a pipeline was purchased and the adventure continued with an expansion of that pipeline being built, with the total cost likely to exceed $34 billion.
On the other hand, the various tax credits that have been announced in recent budgets will amount to tens of billions of dollars. I don't have the exact figures, but we seem to be getting close to the same amounts.
The only caveat I would put to that analysis is that the government could decide to sell the Trans Mountain pipeline and its expansion and presumably reap the benefits of that sale. Will those benefits be more or less than the cost of acquisition and expansion? We think they're probably going to be less, so we would suffer a loss. However, the purchase and expansion costs must also be considered in relation to the profit from the sale, if there is a sale, at some point.