Of particular interest is their page showing live feeds from cameras set up to view NLC at www.iap-kborn.de/Overview.313.0.html?&L=1. Note they have Cameras as far south as Spain (excluding Australia !) - unfortunatly none in the UK.
A description of the network is here. They appear to use Canon G6 powershot cameras with computer control. These of course are no longer sold. If you are thinking of building something similar I have read a post on some Linux software (Entangle)that the latest powershots are very restricted in their remote control capabilities so may not be suitable.
I could not find any details on the website of what special control software they developed other than the statement on the web page above. My Canon 10D seems to cope with Auto Exposure reasonably well when taking time lapse of the twilight and night sky - there is some evidence of shot to shot variation in exposure times but I have not identified the reason for this. Not really visible if you view single shots but shows up when yuo convert them to a movie.
A look round the web shows the last Canon Powershot that you could control by a remote computer was the G10 which may explain the G10's in the list. I presume that as there is no longer a suitable Powershot available new which is why the otehr sites use the consumer DLSR the EOS 550D. At least they will be able to reuse the lens when they wear the shutter out.