Can a R4LC be used to replace a R2LC?
Only the ones from 3rd Rail/ERR. They are programmed for TMCC. Lionel's are programmed for Legacy. I don't think Lionel offers any TMCC R4LCs. You can still get any version of R2LC from Lionel though.
The ERR supplied R4LC-C08 will replace the R2LC-C08, it has the same functionality.
Thank you Pete and GRJ