As one of the sad co-owners of the aircraft, I am at least happy to report that neither pilot was injured.
It appears from having talked to the crew, that this was a classic case of a multi-factorial accident, culimnating in a failure to check three greens on short finals after a practice asymetric approach.
The CFI instructing had 20,000 hours, which just goes to prove the old adage, there are only two types of twin pilots, those who have landed gear up, and those who are waiting to land gear up.
The main reason for the lengthy runway closure seems to have been, that the recvovery services, had insufficient equipment to easily lift the aircraft.
Thankfully everyone walked away from this.