Edmonton has 6 shops / coffee / snack bars built into train stations along their LRT and bus network, plus new ones opening. If I recall, Calgary used to have a few, but does not have any as of now. Many other systems in the world offer retail in transit stations, this is not a new idea, but perhaps one that requires a certain level of ridership and customer-expectation to be successful.
With the enormous ridership we have, could it be a time to look at offering these kind of spaces?
I could see this be a big draw for transit users to pick up some basics or a coffee shop at the busier stations. Even something like a Shoppers could work if they had enough space at certain stations.
Here is a description of Edmonton's service.
http://www.edmontonjournal.com/story_print.html?id=10312043&sponsor=