Theres a picture on the Glastonburyabbey site, of the large egg "fertility" stone by the abbey kitchen. Also my small egg stone which was in the main part of the the abbey amongst some fallen stones. Does anyone know anything about that?
I think the simple answer to your question, moss, is "no".
All we seem to know is that the egg stones are hatched out of the local landscape and we've no proof of what they've been used for.