The simple answer is NO
The long answer as I understand it, is that two versions were produced, the North American version which was used with the PSTN (Public Switching Telephone Network) and a European version which was ISDN for some countries. As far as I am aware it was never sold in the UK mainly because ISDN was only really used by businesses in the UK.
B&O did produce an A/B switch which was an adapter box which converted digital signals from ISDN to analogue signals to be used by other analogue phones. It would mean you could make two simultaneous phone calls one from the Beo 3 ISDN and one from an analogue phone connected to the converter box.
If you really want to use the Beocom 3 ISDN, then your only option would be a converter, one such product is HERE but quite an expensive option and in my view not really worthwhile.