It is already known that the Dawn Engine by Eidos Montreal is an heavily modified version of the Glacier 2 engine
The Foundation Engine by Crystal Dynamics is still supported by their respective owners and was even used by Eidos Montreal, even after the release of the Dawn Engine, which became Shadow of the Tomb Raider using a modified version of the Foundation Engine.
If Dawn Engine is really related to the Foundation Engine in any way then I strongly believe that they would have used the Dawn Engine instead.