I have a customer who ported all their numbers over to a PRI, so the faxes had to go on to an analog extension in the system. DID calls into the system work fine, but outgoing faxes (and calls with by butt set) get a busy signal upon going off hook. As a workaround, I have outgoing calls going out on the still active Loop start lines. What am I missing? Also, I have automatic trunk seizure enabled for these extensions.

Are you using the same trunk access settings as your digital sets? Also check COS settings for the analog ports.

I would also check your mapping.

I have the same COS and trunk group as the digital sets. Here's another funny part. If I direct select a channel on the PRI using #9xxx with x being a channel number, I can only dial 3 digits before the channel goes busy. Weird.
The only thing I can think of off the top of my head is that the software is 6.03 and not the latest, which was 7.3x I believe. Looking at some old release notes, there were issues corrected in regards to PRIs although they don't address this in particular.
All this is a moot point anyway as the customer never wanted the fax numbers ported to the PRI to begin with and will be coming off the Aspire asap.

I would check the hotline for that port.

One step ahead of you on the hotline. Tried it both with and without.

Check your outgoing caller ID for that port. It can only be a couple things.