Here is the official word;
e) GENERAL TEAM CLASSIFICATION
The general team classification is determined by adding each team's best three individual times for the prologue and every stage.
In the event of a tie in the general classification, the order of teams is determined based on the number of stage wins by team, then their number of second places, and so on until a number of places obtained by one of them enables them to be finally placed.
A team reduced to fewer than 3 riders is eliminated from the general team classification.
Sounds like Don hit it on the head.
Andrew