I have a TiBook 867 running 10.2.4 and a StarTac w/service through Verizon.
I don't have a cellular pc card, so I can't tell you about that, but I did get connected via the StarTac. . .
I purchased a StarTac->USB cable from thesupplynet.com ($60, here's the
product page).
After connecting the StarTac to the PB via the cable, the phone was not automatically recognized (I half expected it to be recognized, as I had read that the Motorola phones were supported in 10.2). The CD that came with the cable contained a driver that looked like it was intended for OS X, but after I installed it, the StarTac was still not recognized in my Network system prefs.
What I ended up doing was following the instructions on this great page written by John Chang:
http://homepage.mac.com/jrc/contrib/mobile_office/
I downloaded the AppleUSBCDCDriver Patch (link is on the page above), even though it said that it was for 10.1. After I installed that patch, my phone was detected as a new network port.
I then followed the steps outlined on John Chang's page (downloaded the modem script, set up the phone number/username/password). It works fine now, even if it is rather slow!
Hope that helps.
Jen