You can not use any USB device to connect the PS3 to the internet. You can only use a Broadband Cable or Broadband DSL (wired or wireless) connections to connect to the internet on the PS3.
Even a regular modem connected with a USB cable to the computer will not work. Ethernet connections only.
You can not connect to the internet using the USB ports on the front of the PS3 system. This means you won't be able to connect online using USB wireless adaptors or cell phone USB adaptors with the PS3 system.
If the t-mobile dongle allows you to share your internet connection you might be able to use "Windows Internet Sharing" and a "cross-over" Ethernet cable to connect the PS3 to the internet.