For all the talk about free market economics and small business one hears around here, I'm a little baffled as to why the solution to a high demand for a scarce resource isn't to increase the price for that resource. If somewhere is fully parked with a bunch of cars, it's a problem for people who want to park there whether they are Cars2Go or just a bunch of cars parked to stay. The main difference is that the Cars2Go are offering mobility to thousands of people, while the other cars offer it to only one.
In fact, that's city policy already -
rates for street parking are being adjusted on a quarterly basis, up if an area has too many cars trying to park there and down if an area's parking is too empty.
As of January 1, only one area in downtown was consistently over capacity on weekdays; "Downtown Core 4C" between 7th and the CP, 4th St W and 1st St E. (Area 4D west of there to 8th St is overparked until afternoon, and during the lunch period Chinatown, Eau Claire, Mission and Kensington are also overparked.)
The facts on the ground seem to be that with occasional hot spots, central Calgary currently has priced parking to the point that there is spare capacity. (Of the 27 areas and 5 time periods, 36% have excess capacity, 9% don't have enough, and the remainder are about right.) If we want fewer cars parked on the street, we should keep increasing the prices. I think Car2Go could decide whether or not to pass on the cost to users or not; they are capable of doing so (parking at the airport lot has a hefty charge). It seems odd to suggest that the City should dictate how a business should charge their consumers; certainly there are complaints about it in the taxi sector.
I'm also not sure that passing on the fees is actually the best policy - if Car2Go charged users an extra $2 to park downtown as an example, then the trips that would be least affected would be people commuting to the downtown for a long stay, while people who were just making a quick stop would be more likely to be dissuaded. Yes, the total number of Cars2Go would be reduced, but it would disproportionately be the short-stay users who frequent the businesses complaining about Car2Go in the first place.