the last i remembered, i was day 1 in hk/my company and i managed to get an account opened. i remembered the company's proof of employment was required, plus the typical HKID, Passport stuffs. If you tend to use the phone to conclude transactions, and u decided to use both, then be reminded that they will sometimes use either mean for verification of you, or ask you 'what did you use to open your account, ID or passport' etc... that can get tricky if you are back in your country and don't carry your HKID around anymore.
Credit card was trickier. I think I managed to apply for mine fairly quickly, they probably did ask for my employment contract (as I didn't get any payslip yet) and the approval was given within 1 or 2 weeks.
This second round (i.e. i went back sg, and came hk again 3 years later), my credit card application was smooth. Citi approved it within 1 day (standard docu applies, resi address proof [service appt contract shown], employment status [contract shown to them]). But according to my fren at the credit bureau service, that's probably because I had a credit card previously when i was here and didn't bail on them, so that gave me advantage for issuance approval.