I'm pretty darn sure this is IR.
The faucet itself is confirmed to use a IR detection method to detect your hands via a small window on the front of the faucet.[Link: etnasupply.com]
Based on the statement in the linked manual "In order to adjust the sensor with a remote control, you should hold the remote control straight in front of the sensor at a distance of about 4” (10 cm)." - I've got to assume this is IR.
Otherwise in a commercial facility, I'd think a RF remote could wreck havoc on a bank of toilets or faucets... ;-)