Someone

##### Head Asterisk ####

;;;;;;;;sip.conf

[userA-inbound] ; calls from remote out userA context
username=userA
type=friend
secret=letmein
qualify=500
port=5060
nat=never
host=dynamic
dtmfmode=rfc2833
context=userA
canreinvite=no
accountcode=userA

;;;;extensions.conf

[incoming]  ;incoming calls sent to remote host
exten => _5551234,1,Wait,2 ; Allow for PRI to grab info in facility
exten => _5551234,2,Dial(SIP/${EXTEN}@n5yzv),60)

[userA] ;outbound calls
exten => _210NXXXXXX,1,Dial(${TRUNK}/${EXTEN})
exten => _210NXXXXXX,2,Congestion


##### Remote Asterisk  #######

;;;;;sip.conf

register => userA:letmein@172.16.0.1:5060/5551234

[userA-out]
username=userA
type=peer
secret=letmein
;qualify=500
;port=5060
nat=never
host=172.16.0.1
;dtmfmode=rfc2833
context=userA
canreinvite=no
accountcode=userA

;;;;;; extensions.conf

(incoming calls accept whatever...)

[userA]
exten => _210NXXXXXX,1,Dial(SIP/${EXTEN}@userA-out,60,rwW)
exten => _210NXXXXXX,2,Congestion