I have noticed that the cable box has a USB port on the back. The install tech also said this device uses an IP address.
Is it possible to control the cable box either via the USB cable or through the network?
Well, first thing first, what is the make and model of your FiOS cable box? That information is going to be key in figuring out whether you can control your box from a computer. Also, what kind of control are you looking to do?
I know that some cable boxes (usually older ones) could be controlled by a serial port or firewire.
My guess is that the USB port on the box is a feature that installed in the hardware, and it's up to the cable company to decide if they want to turn it on or not. My old ReplayTV DVR had a USB port that wasn't activated, so it didn't do anything but power my cheesy USB Lava Lamp. Even if it is activated, most likely it wouldn't be able to control the box anyways.
You could probably get an IR blaster to control it with. An IR blaster is a (typically) usb device that sends out IR signals that match those of a remote control. So it can talk to your STB, and the STB wont know that its not a remote. Its tough to recommend a specific model without knowing what kind of STB you have, but a bit of googling or newegging should be able to sort that out.