The Wii U Pro Controller connects using the same procedure as a regular Wiimote, except it has no option for "temporary" syncing (the 1+2 method). Authentication/pairing is still optional, the controller can work without it but it must be performed at least once (and the created link key retained) to enable "one-touch" reconnection.
Information gathered from linux "hcitool info"
Device Name: Nintendo RVL-CNT-01-UC
LMP Version: 2.0 (0x3) LMP Subversion: 0x1d8d
Manufacturer: Cambridge Silicone Radio (10)
Features: 0xbc 0x02 0x04 0x38 0x08 0x00 0x00 0x00