http://www.cars.com/scion/fr-s/2013/...s/?revid=58456
"Scion spokesman Craig Taguchi says an all-season tire will arrive at a later date."
I haven't seen the FR-S owners manual, but based on the FR-S maintenance manual I would guess it may be similar to the BRZ manual.
Subaru's owner manual doesn't mention temperature and says:
"summer tires are inadequate for driving on snow-covered or icy roads. For driving on snow-covered roads or icy roads, the use of snow tires is recommended."
The following quote either lacks context or was added by Subaru's lawyers:
"Do not drive in excess of 30 mph (50 km/h), regardless of the type of snow tires being used."