So, on the surface, you’re screwed… but are you aware of any issues with the pipe? Any previous leaks reported? Any maintenance work on them?
Is the pipe in question in a heated part of the home?

If you can prove any type of negligence or Faulty repairs then maybe you have a shot

Also… it burst in the apartment upstairs?… why did it burst? Did they clog something due to negligence? Was their apartment heated properly?