Thanks for the replies guys. The list trace on my station when I dial the attendant gives:
14:05:11 active station 27962 cid 0x18d4
14:05:11 G711A ss

ff ps:20 rn:1/1 10.10.220.10:2440 10.10.222.21:3116
14:05:11 xoip: fax

T modem

T tty:US 10.10.222.21:3116 uid:0x8ac7
14:05:13 dial 35000
14:05:13 term announcement 32911 cid 0x18d4
14:05:13 active announcement 32911 cid 0x18d4
14:05:13 xoip: fax

ff modem

ff tty

ff 10.10.222.21:3124 (igc)
14:05:13 xoip: fax

ff modem

ff tty

ff 10.10.110.23:2324 (igc)
14:05:13 hear annc board 03B03 ext 32911 cid 0x18d4
14:05:17 denial event 2309: Drop call codec mismatch D1=0x7f000012 D2=0x18d4
14:05:18 active announcement 32995 cid 0x18d4
14:05:18 xoip: fax

ff modem

ff tty

ff 10.10.222.22:2480 (igc)
14:05:18 xoip: fax

ff modem

ff tty

ff 10.10.110.22:2772 (igc)
14:05:18 hear annc board 03B03 ext 32995 cid 0x18d4
14:05:27 active attendant 38299 cid 0x18d4
so as you can see it connects to the attendant ok, but we can't hear each other. Same thing when I list trace attendant:
14:08:05 dial 35000
14:08:05 denial event 2309: Drop call codec mismatch D1=0x7f000012 D2=0x1993
14:08:06 active announcement 32995 cid 0x1993
14:08:06 xoip: fax

ff modem

ff tty

ff 10.10.222.22:2812 (igc)
14:08:06 xoip: fax

ff modem

ff tty

ff 10.10.110.23:2524 (igc)
14:08:06 hear annc board 03B03 ext 32995 cid 0x1993
14:08:15 active attendant 38299 cid 0x1993
14:08:21 idle station 27962 cid 0x1993
14:08:23 TRACE COMPLETE attendant 38299 cid 0x0
I checked both Tenant set-ups and they have calling permission for each other. While I was there, I also made my site (tenant 1) a member of Attendant Group 2, same as Tenant 2, and gave them both the same Attendant Vectoring VDN. Still can't hear each other. Station to station and agent between both sites is fine, it's just for the attendant that I get silence!!