richms: Not all of them will read from telecom. The bellcore timing is different because the ring is different.
I had serveral cordless phones from the US that would not read the ID back before you could get decent ones here (900MHz analog ones mainly) I think I still have the 2.4Ghz one that nicely wipes out all wifi.
It's not only timing. There are data format issues as well. Some phone makers are guilty of designing to what the major US swiches use not the wider Bellcore Standard. Some references claim that a device that can read Multiple message format will cope with single message as well. I can't remember whether that was true. The initial decoders marketed by Telecom just had stickers covering the Cidco branding and a Telepermit label covering the FCC label.