The Banff airport is open for business ! Parks Canada attempted to close it, (and Jasper) but backed down after a legal battle with the local aircraft owners. You'll see several aircraft tied down at either site.
In saying that, the airport is definitely not for the faint-of-heart, between Elk on the runway, Gopher holes, and windsocks that tend to point at each other, and downflowing air off of Cascade Mtn...it is a challenging strip.