Yes - a laptop can connect to a network using a mobile phone.
The setup will depend on the make/model of laptop, modem, and mobile phone. Sometimes the modem is build into the mobile phone itself, sometimes it's a PCMCIA modem card. Some communicate using IR, some using Bluetooth, some using cables.
Get yourself down to your local consumer electronics store / cellphone store for some advice on that issue.
As for connection, you can
a) set your server up as a RAS (remote access server) - in other words, you dial directly into the server
b) set up VPN - the laptops connect to an ISP of your choosing, then use the established connection to VPN to your server.
Your windows help file has sections on setting up RAS or VPN, plus a google search on "setting up ras" "...vpn" should throw up hundred of walkthroughs.
"Reasonable bit rate" - until GPRS / 3G is rolled out, you'll probably be limited to 9600 baud. <marc>[ul]help us help![li]please provide feedback on what works / doesn't[/li][li]not sure where to start? click here: faq581-3339[/li][/sup][/ul][/sup]