The reason the Russians stole the code was because they tried to buy the software of the yanks but they told them no, so they stole it instead.

I think that the risk of a logic bomb although real, is very minimal, in so much as the Russians in that instance installed the software themselves. The people who keep the country running know that there is a threat so they protect against it, and for that reason I wouldn't imagine the National Grid in the UK to be connected to the web. I also think that governments would take telecom and utilite protection as serious as the countrys nuclear deterent, as it would be just as effective to take out BT's main frame computer as it would be to land a nuclear bomb in London. It would also be very difficult to get a bomb to land on it's target because of early warning radar would have it intercepted. I also don't think any country would be so stupid to spend a fortune defending nuclear instalations, and creating a nuclear bunker in Cardiff South Wales to house British Telecoms mainframe computer to then just look over the chance of someone executing maliciousecode in their IT systems.

I would also imagine that with these systems being monitored 24/7 by a human, that they have a manual over ride switch which would ensure that in any such event the system can be controlled soley by a human operator.