Greetings,
You should be able to use voice translation-rules and apply voice translatin-profiles under the incoming dial-peer for SRST mode.
example could be:
voice translation-rule 1
rule 1 /^\(9\)\(....\)$/ /1\2/
!
voice translation-profile SRST_Incoming
translate called 1
and apply under the corresponding dial-peer.
You could also try to use the " dialplan-pattern" under the SRST configuration and manipulate the digits.
Regards,
Val