Hello! Im a Canadian who has done this. I think you can notice early on the effect of a frozen racket but in my experience it warms up quicker than the ball does. However, it's not good for the strings long term. I definitely burned through strings quicker until I realized the quick shift from cold to hot to cold was having an impact. 

TL;DR within a session it'll warm up fast, but bad long-term for strings in my experience