I work for Rogers and doubt this is the issue as there's other customers that would use way more data and bandwidth than Tesla does. However, it does seem like they VPN all traffic back to the US, as if you use the web browser in the car it and ask who your ISP is, it will show Jasper Networks (Jasper is the IoT platform) and has a US IP address showing usually California as your location. A VPN can only handle so much bandwidth being that it's encrypted traffic so it's more likely that it's the VPN getting congested vs the LTE network, but that's just my guess. Having said that, I'm in Toronto and have not experienced this issue at all.