Offically its not happening.

There used to be companies like VIPBALI that provided this service, you could book it online and they would be waiting at the entrance to the arrivals hall with your name on a board - and they would look after you

from what I can gather and this information is all anecdotal is that the Imigrasi are now running this program (scam) so when its busy it appears that some of the officers stop working their booths - and start patrolling the lines - and when someone says something about the line ups - the expedited service is available for a price

it seems to be more prevelant in the evening bank of arrivals - say from 2100 - when many flights arrive prior to the evening bank of departures from 2200 - 2400.

I am arriving early afternoon in early November- will update with what I discover