Icing conditions temperature range: SAT or TAT?
For the purpose of aircraft limitations, it's TAT for the upper limit of +10C.  SAT for the lower limit of -40C.

Generally once you are going faster (in the RJ, above 230kts) you only need to have cowls on for all visible moisture conditions, and wings only need to be on if actual icing is happening or indicated.  Ice can form on cowls from the temperature drop related to the inlet pressure drop, like carb ice, so the requirements are more conservative for the cowl A/I system.  Cowls are turned on and off way more frequently than wings.