Virgin Mobile has completed its 4G trials in the UK, hitting speeds of 90Mbps both indoors and out. But don't expect EE's 4G monopoly to break any time soon despite the ongoing collaboration between the two companies.

Virgin's mobile business is a virtual operator, carried on EE's 2G and 3G networks, but these next-gen mobile broadband trials weren't related to any extension of that deal. Rather, they gave Virgin the information it needs to compete with EE in both mobile and the fibre-optic business in which EE has sworn to intrude.

The trials have been running since February, in Bristol and Newcastle, and used Small Cells to provide islands of 4G coverage backhauled over Virgin's fibre network. Virgin's fibre already provides backhaul for loads of mobile base stations, for just about every network operator, and the company reckons its metropolitan reach is ideally suited to building its own wireless network, whether that's based on Wi-Fi or LTE.

Virgin Mobile's current offering is carried by EE, the company previously known as Everything Everywhere that isn't even sharing its UK 4G exclusive with its own brands, Orange and T-Mobile. So it is unlikely to let an upstart MVNO get any 4G goodness in the 1800MHz band it owns.

Virgin's trials were carried out at 2.6GHz, which will come up for auction next year, and the trials have enabled the company to work out the costs for national deployment, and thus bid sensibly when that auction comes around.

It's easy to imagine a Virgin Mobile 4G network, using Small Cells in customer homes and bolted to lamp posts around the cities. Punters can roam onto one of the existing 2G or 3G networks when venturing further afield. Virgin will certainly have done the mathematics on such a model and worked out the maximum amount it can bid for a 4G licence.

But even if it doesn't win a chunk of spectrum the trials are still valuable: the winning operators will be scrabbling around for backhaul to carry all that additional traffic - and nothing carries traffic like optic fibre.

Which is why EE, when it launched its 4G proposition two weeks ago, also said it would offer fibre optic connections to 11 million UK properties by the end of 2013. We don't have any details on that, but EE clearly plans on digging up enough road to compete with Virgin and use that fibre for its own mobile backhaul too. It shouldn't be surprising that Virgin is considering an expansion into EE's territory. ®