Choose either route pattern or route group to set External Ph number mask, Calling party transform mask and prefix digits. (not both). Any time you set a calling transform mask or prefix digit at the route group level, every other setting at route pattern is overridden.
If you set Rgroup setting to Default, it will honor settings at route pattern level. (except in cases where you set a calling transform mask or Prefix digits at route group level).
If you set Rgroup setting to On, it will override settings at route pattern level.
If you set Rgroup setting to Off, it will override settings at route pattern level. Calling party ext mask will not be used.
For MGCP gateways, if Caller ID DN is set at gateway level, it will override settings at route list level. If Caller ID DN is not set at gateway level, it will default back to Service parameter settings.
CCIE Voice notes 
Dear CCIE,
What you say is true if you want to mask all phone CLID – but i have customer who wishes only to have some numbers masked and the rest to show Caller ID. i have tested by running the few phones requiring masking through a TranslationPattern to get to the PSTN and setting Caller ID to restricted. However, on site this fails – is it possible PTT is overiding my settings? Can you suggest another method?
Regards, usman patel
you shud use at the phone level.
untick caller id on all phone who doesn’t want caller id to be sent out to the pstn.