Hi Harkonnen
I think it will not be a problem. As you know CEPT has quite rigourously divided the bands 868-870 in different application areas such as for very narrow band , low & high duty cycle etc. and only so called more unstable devices as SAW based oscillators are allowed into a 300 kHz subband.
As for 865-868 MHz, the only allocation yet is RFID and CT2.
CT2 has the ability to dynamically switch operating freq. when it receives interference. When CT2 is dead completely, I guess it will absolutely be no problem to have the quiet RX levels you are looking for. Furthermore, CT2 is a freq agile system (not at all broadband). As I understand it is not possible anymore for some time to buy new CT2 equipment, so in a few years time it will be dissapeared completely.
Kind regards
Mike