The answer has been discovered. Cisco TAC finally provided me the solution to the transfering of calls with access code.
What is needed is an H.3232 gateway set-up with an outbound dial-peer pots.
dial-peer voice 123 pots
destination-pattern 4444
digit-strip
prefix 011888888888,,,,,,,,,,123456
port 1/0
Cisco Unity will transfer calls, but sending extra digits across can only happen if you use 3 or fewer commas. Otherwise it creates a disconnect.