In the UK Vodafone and Orange on the one hand and T-Mobile and 3 on the other are trying to find ways to decrease their CAPEX and OPEX of running their 2G and 3G radio access networks (RANs). Early announcements said that they intended to share not only the base station sites, antennas and feeders but also the base stations and the radio network controllers. Looks like in the meantime, Orange and Vodafone are likely to only share base station sites. This is not a particularly new approach, as in many countries sites and masts are often used by two or even more network operators.
With the quickly growing use of 3G networks for Internet access I even wonder if base station sharing makes sense at all!? After all, sharing a base station instead of using two individual ones decreases overall capacity. Sure, a single base station could be upgraded to have an individual transmitter for each operator, but not much beyond. Also, the backhaul link would have to be upgraded to support this. With usage increasing significantly these days I wonder if that wouldn't create a bottleneck rather sooner than later as operators can probably not add any additional hardware to such base stations to increase capacity later on.
So even if there should be some cost savings from this scheme, I wonder if the inflexibility this creates negates the effect. Cost for software and hardware upgrades to achieve higher speeds for example would have to be shared between the two companies. So if one is happy with the current performance of the network but the other is not, that would pose a serious issue for the party who's network is close to overload.
Maybe a better way to save costs is to open the radio networks for national roaming in areas which do not require a lot of bandwidth such as on the countryside for example. Operators could then agree who builds the RAN in which area and invites others to share the infrastructure. Not sure if national telecom regulators would be happy about such deals as it surely has an impact on competition, just as the original plans for RAN sharing.