With the system for distributing pairing information to RDPs that was installed in the late 80s, there was a shortage of communications ports and they were all used up by the mid 90s (NSL airports had to use some data splitters to get information to some of their newer systems). The sytem was replaced a couple of years ago, so there should not be a capacity problem - no doubt NSL will sell the data for a small(?) fee.
The input side is more problematic, but the Single European Sky Regulations presumably will mean that NATS will have to offer input and output data facilities to non-NATS airports on the same terms as they are provided to NATS airports and the interfaces will have to conform to some interoperability rules. HOWEVER, the current systems are limited and use arcane interfacing protocols so non-NATS airports will have to wait until they are replaced (and wait, and wait, and wait ...)