From what you describe the wall and tiles affixed to it would be all considered as common property, hence are indeed the responsibility of the owners corporation. The bath though has me guessing a bit, this item and plumbing above floor level are the responsibility of the owner. Is there a shower above the bath or is it separate? I’d just wonder why it is necessary to remove the bath, except if there were some plumbing leak below it in which case it may be your responsibility for that part.