The way I understand it is that ES is only on eligible rates, and presumably your international rate will not be eligible. Some locations may provide an unofficial benefit on top of your entitlement, but from experience SUVs in snow areas go fast and are in short supply, so you are unlikely to get the car you want. Also while warm areas such as Florida and LAX have mostly SUVs in the ES, snow areas tend to have few SUVs on ES -- it really depends on your specific rental location. Chances are you actually have to book an SUV (and its much higher rate) in order to get one. SFO is maybe an exception (if you consider a 200 mile drive to the snow to be acceptable).