I'm sure the lots will still fill up completely. Not that large a proportion park and ride on transit. The only way it will affect ridership if the lots are less than full, which I doubt. Some people will switch to taking the feeder buses, others might even be compelled over the long term to move closer to a transit station (maybe even in one of the TODs that will replace the large surface park and rides and Brentwood and Anderson) or alternatively, closer to work.
Very few cities just give away parking for free. Large surface lots are extremely unsafe (huge vehicle break-in rates - Brentwood being the highest) and are an incredible waste of valuable land that should (and will be) developed into high density. Part of Calgary growing up - structurally, it needs to change to have much more efficient land use - ie higher densities, more mixed uses and better access to transit.
Below - Two TOD Station Area Plans (there are six of these planned in total (Brentwood, Banff Trail, Lions Park, Chinook, Anderson and Canyon Meadows)
Anderson TOD - about 2/3 of the park and ride spots will be replaced in parkades
Slightly outdated digital model of the Brentwood TOD (the plan has changed to a degree on the south side of Crowchild)
