Altimeter subscale setting CAN affect TCAS. Not in the sense that adjusting the subscale directly does anything to either the TCAS unit or the transponder, but I'm sick of explaining myself over and over.
I respectfully suggest that you have a look at the relationships between radar displayed alt, radar data processing, and mode c, as described in this thread. The key point being that the RDP expects you to have the correct subscale setting.