[130166]

Depends rest of your dialing plans, but maybe this help you.

Dialplan rule:

prio: ??? (depend other rules)
pattern: _XXXXX or _XXXXXX or both? (I do not know how much digits in halifax)
comment: local
Replacement: 01422${exten}

warning: works only if you have not other dialplan rule with 5/6 digits, in that case you can give possible starting digits in pattern above or in other rule

or:
prio: ??? (depend other rules)
pattern: _Z. (every number not starting with zero)
comment: local
Replacement: 01422${exten}