[nick_you_owe_me_one]
exten => _X.,1,NoOP(Starting our dialout)
exten => _X.,n,Set(location=rugby)
exten => _X.,n,Set(dialstring=SIP/${EXTEN}@cisco_trunk_1)
exten => _X.,n,GoSubIf($[${EXTEN} = 911}]?sub_get_location_emergency,s,1:)
exten => _X.,n,Dial(${dialstring})

[sub_get_location_emergency]
exten => s,1,NoOP(Getting our emergency services location);
exten => s,n,Set(dialstring=${IF($["${location}" = "nick"]?Zap/1/${EXTEN:1}:${dialstring})});
exten => s,n,Set(dialstring=${IF($["${location}" = "rugby"]?Zap/1/${EXTEN:1}:${dialstring})});
exten => s,n,Return();