No you can only have 1 base connected to the track. That's the law.
A TMCC base can be connected serially to the 990 so that both a Cab1 or Legacy Cab2 can be used together. A Base 1L and Legacy Base should never be used together.
I was trying to operate 2 TMCC cars at once without having to change the ID's. Kind of defeats the purpose of Command Control.