asterisk users - Aug 2005 - How to get long distance carrier to provide separate billing for several companies that share a PRI to LEC?

I have a single PRI to our local telco that is shared by
multiple companies.  I would like to find a way to get our
long distance carrier to provide separate billing for these
companies.

I am currently calling Authenticate() to collect an account code
which is written to the call detail record, then I estimate the
charges for each company by parsing the call detail records.
This doesn't work well since we are billed different rates for
intrastate/interstate/international calls and I don't want to
keep up with rates for every NPA-NXX.

Is there a way to pass the account code collected by
Authenticate() to the long distance carrier over PRI?

I can get the long distance carrier to enable account codes
on their switch instead of using Authenticate() in Asterisk,
but this doesn't work because DTMF digits are lost unless
they are dialed *very* slowly.  The DTMF digits are being sent
out-of-band (RFC 2833) by Cisco 79XX phones over SIP.  The long
distance carrier collects the account code after the ISDN SETUP
but before the CONNECT.  There are no problems with DTMF once
a call is connected (so I don't think this is a codec issue).
If I use ChanSpy() to listen to the DTMF being sent to the
l/d carrier I can hear dropped digits unless they are dialed
very slowly.

Any help would be appreciated.

Thanks,
Will Scales