@ Ian Ferguson
When you fly out of Heathrow, and have just missed the BA Flight, do you expect to be able to catch a KLM one cos it's there?
Do you expect your neighbour to give you a lift to work, just cos there's a spare seat in his car?
You pay's yer money and takes yer choice - if O2 have poor signal where you want it, tough! You should have taken a Vodafone contract, deal with it!
Do you actually understand the technical aspects of network sharing, not to mention the business impacts of getting into bed with your competitors. Do you imagine you can simply bolt an NSN base station to an NEC one or an Ericsson to a Huawei? Do you imagine that 3 would want to invest years of planning in a scalable backhaul solution then let Vodafone just piggy-back onto it after their own plans bombed?
The deal is basically just a reaction to all the NiMBYs who don't want new sites closeby but bitch about the voice quality. They're sharing Cabins, not Cabinets since the contents are pretty much invisible to the landlord, and kit should be locked away from 'accidental' interference.
Of course it's only some kind of frame agreement, so the sole 2 900MHz spectrum owners might not share a single switch room in support of this PR.