If transferring:
Security: has a fast track lane: they took my *G economy BP (without a *G card), so I imagine they'd take a business class BP there.
Transfer/immigration:
- If departing internationally: BP check: there is a fast track lane but it was closed, the main queue only had 3-4 people
- If departing domestically: immigration, I didn't see whether there was a fast track, but it looked quite empty.
Note: every time I've been through the place only has about 10-20 passengers in it. I don't think many people are transferring.