Will mobile network sharing lead to separation?

This news from Thailand again brings up the matter of separation in wireless networks. Thai Mobile seems to volunteer the building of the nation's first 3G network, to which it will offer open access to all operators.

Other recent news around mobile network sharing:

• Vodafone UK and Orange UK plan RAN sharing (3G and 2G) to reduce capex and opex by 20-30%.
• Hutch Essar and Bharti plan infrastructure sharing, to be supported by the regulator.
• Nokia's solution is expanded to supporting up to 4 operators.
• Yoigo (TeliaSonera) and Telefonica Movistar plan antenna sharing.

(Now, it is important to realise that sharing may be done at different levels: sites (towers), antennas, RAN, backhaul.)

Some observations, beyond the obvious cost savings target:

• Similarly, operators are teaming for mobile TV (be it a shared DVB-H network, wholesale access to Qualcomm's MediaFLO or any other technology). So, why not for 3G as well - or for that matter: for 2G (not to mention 4G)? As in fixed, sharing and separation make a lot of sense in an IP-based world.
• Differentiating by touting network coverage (as Verizon Wireless still does) will become a thing of the past.
• So, operators will need to make sure they can differentiate on the services and applications level.
• If network operations are to be separated, a new (natural) monopoly will arise. As long as existing service providers are deemed to have SMP (significant market power), this may give rise to new open access obligations at the network operator. On the other hand, the rise (not the fall) of MVNOs could preclude this (what will the difference be between MNOs and MVNOs anyway)? However, spectrum will always be much more of a scarce resource than anything equivalent in the fixed world (duct access, access to sewers, etc).