Hi Paul!
You should be able to dial e164 numbers in the IVR. With the right serch rule on the VCS
this should hit your TPS. An other option could be dedicated dial in numbers from ISDN
so you can direcly match it to a URI or to use (legacy) the IPGW, so you could use even
a text based, tms driven phone book. I really liked the IPGW, to sad it was retired.