Seeing as how this is the PADI ice course, there will definitely be more than one person in the water (although I don't believe it needs to be an instructor on any dive, just a current DM or above) and it can get quite dark depending on snow cover, so a light is a good idea. Just because someone tells you conditions are "usually" one way, doesn't mean you should ignore being prepared for them to be otherwise.
Using the lights to signal presumes that the other divers know what light signals are - since the night diving course is not a prerequisite for the ice course I suggest not making that assumption. And just because you tell the other divers what the light signals are shortly before jumping in the water does not mean they will retain them when under the ice (they likely have enough on their minds and enough stresses already).
Have fun, this is a great course to take.
Using the lights to signal presumes that the other divers know what light signals are - since the night diving course is not a prerequisite for the ice course I suggest not making that assumption. And just because you tell the other divers what the light signals are shortly before jumping in the water does not mean they will retain them when under the ice (they likely have enough on their minds and enough stresses already).
Have fun, this is a great course to take.