For an Underworld Unleashed tie-in this issue had very little to do with that crossover. In fact the only thing that seems to tie in at all is the mention of Neron by Freeze's henchman. No telling what his deal was with Freeze. These days it would be about his wife. But this was from when the comics were purely original and didn't draw their inspiration from outside sources.
This was a pretty entertaining stand-alone adventure from the days when Mr. Freeze wasn't as regular as he is now, and a bit more evil instead of being some guy you're supposed to feel sorry for.