will airport extreme card work on other wireless systems

It's not a question of the cable service as much it is the hardware used to connect.

You need a wireless base station conected to the cable router.

There should be no issues with the majority of the popular wireless base stations available.

To setup OS X, follow the instructions:

http://www.simplehelp.net/2007/04/17/how-to-connect-your-os-x-mac-to-a-wireless- network/

"AirPort" is just Apple's marketing for 802.11? protocols, commonly called WiFi. "AirPort Extreme" is used with the 802.11g standard and higher speed standards by Apple. An AirPort Extreme card will negotiate the best common protocol between itself and the base station (Apple's term for the router). If the router offers multiple wireless networks at different speeds, you'll be able to choose an appropriate one with the AirPort Extreme card.

The only incompatibilities are actually on Apple's end, as a card marked "AirPort Extreme" cannot be installed in a slot in a Mac for an "AirPort" card, and vice-versa. The slots are electrically and physically incompatible.

Almost all WiFi devices - AirPorts included - will "downgrade" to a slower common protocol if needed. This can cause unintended consequences with some systems, as the router may downgrade every device to the slower speed if one slow device connects.

Note, Airport Extreme on PowerMacs is limited to 802.11g. If you find you get a router that is 802.11n, and have devices that need 802.11n speed, they should be on a different wireless network. Otherwise you can set the network to be 802.11n and 802.11g for both 'n' and 'g' devices to hook up to it from the router in question. Be sure the PowerMac in question does support Extreme, and not just the original Airport by visiting this article:

http://support.apple.com/kb/ht1621

And identifying your Mac in this article:

http://support.apple.com/kb/HT3082

If you can't find your Mac on the article, go to Apple menu -> About This Mac and tell us the Machine ID. If it is a notebook, the name of the machine is on the screen frame. If it is a machine with a display and a built-in optical drive that has no name, it may be an iMac. That is significant as well. Since you posted in the PowerMac forum, without telling us your machine, we can't help you further until you do.