Could it be that the call-taker in both ComCens had more information about the MVA traffic risk
I do not know all of the information. But it could be that the tree is a major traffic hazard on the dual carriage way highway that has a lot of semi / b-double truck traffic.
My thoughts are it is better to protect and prevent an accident than turn out to a RCR.
If that is the case and MFS said no to turn out, then CFS could be on scene faster than SES. So to protect and prevent, this seems reasonable to me.
You turn out both brigades to a RCR in that location I assume, why not both to prevent a MVA ??