Ebola is an RNA virus.
Knowing how fragile RNA is, and the wide range of stability of proteins, I doubt that virus would be able to survive in those conditions. When you work in a lab, for instance, extracting RNA from Ebola viruses for PCR analysis, you go through a pretty ornate ritual to remove from the environment anything that could damage the samples. You wash the glassware with a special detergent, and rinse it with water that has been processed to remove anything that can damage RNA. You wash down all of the bench surfaces with a chemical to destroy anything that might damage RNA. You buy disposable lab supplies that are certified RNase and DNase free. You dedicate lab equipment for the purpose of analyzing RNA, and you never contaminate that equipment by using it to analyze any other type of biological molecule. People who work with RNA are extremely paranoid about anything that can destroy it, because it is so fragile. Your skin is saturated with enzymes that kill RNA, and those enzymes tend to be all over. Even when you put RNA into a special stabilizing solution, it has a shelf-life--about one month at -20C. When you put the purified samples in a -70C or -80C freezer, they last indefinitely--but once you remove them, you have to complete your analysis on them, because the RNA is not stable enough to freeze the leftovers for further analysis.
Proteins range in stability, but even the extremely stable proteins do not survive multiple freeze-thaw cycles. Changes in temperature are very destructive to any biological molecule.
Another RNA virus is rabies, which is endemic across the US. I have never heard of a case where rabies was transmitted by droplets of frozen saliva. Certainly, if rabies could transmit in that fashion, we'd have a lot of cases where someone out tramping through the snow in the winter kicked up a powder, or brushed their shoe, or otherwise made contact with virus-laden bits of ice. If rabies could transmit in that fashion, rabies would be a huge problem because of its endemicity. No one would know they'd been exposed, and so wouldn't get the prophylactic treatment. But rabies is not transmitted like that--the only way to get rabies is through direct contact with the saliva of an infected animal. All it has to do is enter through a break in the skin.
Usually we are lucky to have more than one or two thaws in a winter. Maybe global warming is cause for hope..
Rabies is a poor comparison, especially when you consider that a human would have to cut the trail of an infected animal and the odds of that are pretty slim, and even more so when you consider the odds of that particular patch of snow being contaminated.
My curiosity with Ebola, though, lies in the concept that humans congregate unlike the more territorial rabies carriers, and share space. Those shared spaces would have a significantly higher possibility of fomite contact, frozen or otherwise, and cold has been shown to preserve the virus. I even cited ER entrances as an area of possible concentration, due to the nature of the traffic there.
While winter is ertainly not at -70C ambient, but I have been in -40 (same temp either scale) and colder weather numerous times, and yes, life goes on despite the cold. I have seen a month here where the high temperature for the month was zero Fahrenheit (on one day, for about an hour), so this isn't the more temperate winter of much of the lower 48 I am talking about. Our snow sublimates during the winter, but seldom melts until spring.