I have started to always put the transponder to XPDR when the push/taxi starts because I don't bother remembering the airports where this is a requirement or not.
If the airport isn't equipped with this new transponder surface monitor system (A-SMGCS?) I have been told that "my" squawk won't bother anyone.
And the data sent out are not capable of trigging TCAS equipment (XPDR-mode)