You can successfully get an Ericsson PBX with H323 available on it trunking with an Asterisk server.
Using Asterisk 1.2.7.1, asterisk-oh323 0.7.3, and FreePBX.
Initially we tried using the H323 channel driver included with Asterisk, but we had problems with calling from Asterisk to Ericsson - there wasn't any audio being sent. Calling the other direction was fine however.
Then we tried using the OH323 channel driver instead - that worked fine with except for Caller ID from Asterisk to Ericsson.
Here is our configuration from the /etc/asterisk/oh323.conf file:

[general]
listenAddress=0.0.0.0
listenPort=1720
tcpStart=10000
tcpEnd=20000
udpStart=10000
udpEnd=20000
fastStart=yes
h245Tunnelling=yes
h245inSetup=yes
jitterMin=20
jitterMax=100
ipTos=lowdelay
outboundMax=100
inboundMax=100
simultaneousMax=100
wrapLibTraceLevel=0
libTraceLevel=0
libTraceFile=stdout
gatekeeper=DISABLE
gatekeeperTTL=600
userInputMode=TONE
amaFlags=default
accountCode=H323
language=en
musiconhold=default
context=incoming-oh323-custom

[register]
alias=asterisk
alias=123
context=all-aliases
alias=ASTERISK
alias=666
context=more-aliases
alias=665
context=all-prefixes
gwprefix=00
gwprefix=01
context=more-stuff
alias=664
gwprefix=02

[codecs]
codec=G729A
frames=2


The trunk configuration line (as used by FreePBX) was as follows:

OUT_4 = AMP:OH323/$OUTNUM$@10.2.1.201:10040

The IP address is your Ericsson IP address and 10040 is the H323 port that has been configured in the Ericsson box.
We tried using the default 1720 port but it had issues and our Ericsson technician changed to the 10040 port which is currently working.

To get a ring tone working when calling from the Ericsson to extensions on Asterisk, we had to change the incoming OH323 dial plan context to a custom context and manually play the ring tone down the channel.
The context we created in extensions_custom.conf was as follows:

[incoming-oh323-custom]
exten => s,1,NoOp(Incoming OH323, ${DNID})
exten => s,2,Answer()
exten => s,3,Playtones(ring)
exten => s,4,Goto(from-internal,${DNID},1)
exten => s,99,Hangup


There is a single drawback we are working on still.
Caller ID from Asterisk to Ericsson doesn't show up (it's fine the other direction however).

Apart from that we now have least cost routing over the WAN links and full access to internal numbers in both sites.