I just had a quick search about temperatures in a crematorium. Around 800 °C. A structure that can withstand that sort of temperatures is probably also able to withstand exploding batteries. If I remember the Galaxy 8 disaster, they go pop and then it’s just mostly a chemical reaction releasing heat and gas. 30 batteries might be a lot. It may not end up destroying the place but it will possibly leave it in need of repair.
Why do you want to create this sort of fireworks show in a confined space where under normal circumstances nobody will be present to witness it?
I think they are doing that wherever possible. Schools and ICUs moved underground where it is possible and necessary. In war time, you don’t have the time or the money to finance big infrastructure projects unless there is a clear military advantage to them, e.g. reopening a bridge. And I wouldn’t be surprised to learn that EU funds have already been used to strengthen civilian infrastructure underground in some areas of Ukraine.