I believe the main justification is that the greatest risk of airproxes is believed to involve aircraft infringing CAS around high density operations, ie. the TMA. The proposed solution is to provide a LARS covering said area. Will that prevent infringers? May be, we'll just have to see I suppose. Anyway, I suppose NATS' argument would be that if it might prevent incidents, it's worth a go. Nice to see someone putting money towards a safety initiative with perhaps no immediate commercial gain visible, wherever the money comes from.
Never thought I'd say that about NATS!