This church existed long before the Episcopal Church, let alone the diocese. Unless the vestry actually signed over the deed to the diocese at some point, the building and land should be exempt from the Dennis Canon. I believe that has been found true in some previous cases involving pre-Episcopal era properties.
I can’t divulge the church as the case is about to go to court. It is a similiar situation belonging to the Church of England first, and the members are very leery of what might happen in court. We have friends back East, and they feel that they may not have a legal leg to stand on.