I know we only had two or three games called off at Caley Stadium in the eight or nine years before the USH was installed - Morton and Raith ring a bell.
I'm not sure that both those two were even due to a frozen pitch, I think at least one was due to snow and/or weather on the A9 (having driven up all the way and run into a whiteout at Drumochter I got a call five minutes later to say game off!).
And there was the New Year Derby off in 2003, when I got the call around Carrbridge after seven hours driving, but I can't remember if that was in Sneck or Dungwall.
I'm pretty certain the ratio of call offs is higher since the USH went in, but that could just be down to more bad weather than before.