You guys are really top notch! I did not expect to get this much valuable information. I did some more research as well and it looks like Cingular is ready to roll out their version of PTT very soon. Here is an article:

BlackBerry Cool » Cingular To Launch Push-To-Talk Phone Service

And Cingular may also be set to get a PTT version of the BlackBerry Pearl?! Here is a link:

Cingular: Push-To-Talk Blackberry Pearl Coming In 4-8 Weeks - RIM Blackberry Forums - Pinstack.com