I ended up doing what Ernie Gm7kbk suggested, which is basically running the MB_BM through DMRGateway to change TG9 to my target TG.
Works great! Now I have audio both ways.
Debug=0
# BrandMeister
[DMR Network 1]
Enabled=1
Name=BM
Address=3103.repeater.net # 74.91.118.251 Change to the address for your Master
Port=62031
# Local=3352
# Local cluster
TGRewrite=1,9,1,9,1
# Reflector TG on to slot 2 TG9
# TGRewrite=2,9,2,9,1
TGRewrite=2,9,2,311620,1 # ROUTES TG9 to target TG on BM
# XLX TG 6 on to slot 2 BM TG12345 # Change 12345 to desired BM TG
# TGRewrite=2,6,2,12345,1
# Reflector control command slot 2 94000->4000 to 95000->5000
PCRewrite=2,94000,2,4000,1001
# Echo on RF slot 1 TG9990 to network slot 1 9990
TypeRewrite=1,9990,1,9990
SrcRewrite=1,9990,1,9990,1
# Reflector status returns
SrcRewrite=2,4000,2,9,1001
# Pass all of the other private traffic on slot 1 and slot 2
PassAllPC=1
PassAllPC=2
Password="passw0rd" # Make sure the password is passw0rd for BM
Location=1
Debug=0
MB_BM
MMDVM_Bridge.ini
[DMR]
Enable=1
ColorCode=1
EmbeddedLCOnly=1
DumpTAData=0
[DMR Network] ; to DMR
Enable=1
Address=127.0.0.1
Port=62051
Jitter=360
Local=62052
Password=passw0rd
Slot1=0
Slot2=1
Debug=0
DVSwitch.ini
[DMR]
Address = 127.0.0.1
TXPort = 32103
RXPort = 32100
Slot = 2
; Slot = 1
MB_XLX
MMDVM_Bridge.ini
[DMR]
Enable=1
ColorCode=1
EmbeddedLCOnly=1
DumpTAData=0
[DMR Network] ; to DMR
Enable=1
Address=45.77.186.5 # IP Address of XLX reflector
Port=62030
Jitter=360
#Local=62033
#Password=passw0rd
Password=PASSWORD
# for DMR+ see https://github.com/DVSwitch/MMDVM_Bridge/blob/master/DOC/DMRplus_startup_options.md
# for XLX the syntax is: Options=XLX:4009
# Options=
Options=XLX:4001 # Option for module A
Slot1=0
Slot2=1
Debug=0
DVSwitch.ini
[DMR]
Address = 127.0.0.1
TXPort = 32100
RXPort = 32103
Slot = 2
; Slot = 1
