I brought my baby 65 days old, on 18/03/2013 and they provided on arrival RP for the baby (2 years). They will write the RP number on the passport. you only need to have separate pass port for the new born. Also both Mother and Father need to have valid RP.
After arrival (few days later) I went to immigration along with the application form signed by my company. they put the RP sticker on baby's passport. charged QR 360.
No other documents were needed.

It was 90 days when I brought my baby (mentioned in MOI website). Check on website for any updates. May be they have changed. Hope this helps.