"It's official - Microsoft owns the UK's Government Gateway" say The Register. I'd have to disagree.
The UK Government are doing a lot to improve interoperability between the citizen, local government and central departments. For the most part this is started in something called the Government Data Standards Catalogue, a comprehensive directory of data elements and their validation rules (eg, structured and unstructured addresses, NHS numbers, sex categories [the NHS use six, so it's not as easy as it sounds]). Using that as a basis, you can build up messages to model the business process -- SOAP and WSDL are more than likely to be mandatory for new systems very soon. And so if the messages themselves don't match, at least the data items do, and transforming XML messages is reasonably easy. Some processes are being modelled at a central level and applied across government departments; others are being done by private companies as part of publicly-funded "Pathfinder" projects (which have an explicit objective of social inclusion). The whole activity is being done with both public sector and industry involvement. The upshot of this all is a government using Web Services to achieve joined-upness [a technical term...].
Now where does the Government Gateway come in? The Gateway is supposed to be a few things: partially a portal to all of this, and secondly a clearinghouse to hold the business logic of the transactions, to throw the messages to all the correct places. Lastly it will also provide authentication procedures. Where's the lock-in? I don't believe there is any. The interfaces provided by the local government bodies at least are/will be documented and publicly available. I mean, obviously I worry that Microsoft are going to close all this up, or if not close it up then make an enormous amount of money out of a not completely open system -- but the way I've seen it going so far, the government people working on it are surprisingly clueful and the definition groups impartial and rigorous. [How do I know this? For work, we just built a Web Services based local government Pathfinder. It's all pretty cool.]