Buses don't lead to the economic spinoffs that are the real prize. Having transit to Banff and the airport for Calgarians is the gravy on this turkey dinner economic development project.
Opening this train will be a huge deal in the rail-fan, and rail-tourism community. It will be huge for hotels and conventions in Calgary. It will be huge for the airport - creating a much better connection to our relatively high yielding destination (you don't have to tilt the case by much to make Calgary a more appealing superconnector than Vancouver). It will be huge for Banff, which can now pitch transit oriented hotels, to increase visitation without increasing the number of cars. All those things make it awesome without even talking about transit for Calgarians and Albertans.
The project makes too much sense really, but the benefits are really spread out in a way that isn't entirely capture-able.
And yeah, UPX is bad if you think of it as soley transit. If you think of it as 'this enables more head offices to by in downtown; and enables the convention market to grow; and enables downtown hotel rooms to grow'—then it makes sense. Downtown Toronto had lots its 'close to the airport' credibility.