Now, that may be a bit tricky as your u8x8 object is probably global at the moment, and so any call to Trill::begin() will only take place after that. So, I'd recommend that you ensure that all of the Trill objects' begin() method (which in turn calls Wire.begin()) are called before you construct the u8x8 object, so that the latter will override any pin setting done by Wire.begin().

My guess is that while Wire may do some pin initialisation, it won't care if someone changes that afterwards, as long as you keep using the same bus (0). As SDA0/SCL0 are the same signals used normally by Wire on the Teensy 3.6 - and without any specific knowledge of the library or of the board - I can try to make a guess. However the addresses from 0 to 7 are not used because are reserved so the first address that can be used is 8. shift the value one bit to the right), yielding an address between 0 and 127.

If you have a datasheet or sample code that uses 8-bit address, you’ll want to drop the low bit (i.e. Monolithics (Virtual Wire protocol, but this has not been tested. The Wire library uses 7 bit addresses throughout. The Trill library currently uses the Wire library for I2c communication, so whether that one does any initialisation pertaining the functionality of the pins under the hood, I am not sure. This VirtualWire library has now been superceded by the RadioHead library.

Wire library alternatives