I am Ericsson specialist and do not know NOKIA GSM BSC features, but it must be some prompt command response if there is a interference at the moment when command is issued. Even more, there are statistical features that presents in details what the influence to the system is caused by the interference. For DCS the most probably source of interference is caused by bad cell planning, frequency reuse, height of antenna, bad downlink power control, disabled frequency hopping etc. In DCS, I have no experience about unwanted source of interference, TV UHF-VHF broadcast, jammers etc.