I haven't tried it but does anyone know if its possible to connect a usb cable into the XP8 and connect the other end to a remote using the system and update from there??

I an unclear on what you are trying to say, but I woudl say no.

I usually update the XP8 over the network once I put the initial programming in it. Sometimes you have to click send swice.

What I found with updating the XP8 over the network is that it needs approx 30 sec to 1 minute before it'll accept commands. Maybe it's going through a reset or possible waiting to see if there's anymore info coming. With a USB it knows it's done when the cable is disconnected, for a network update it might have a time delay after receiving the last packet. Sorry...this doesn't have anything to do with my question.

There are two usb jacks on the back of the XP8. If I connected a USB cable to one of those jacks and the other end to ...let's say a T2C, could I send the updated file to the T2C if I (the computer)were plugged into the front USB programming port of the XP8.
The XP8 would act as a middle man sorta speak.

If this isn't possible then what are the USB jacks for?

The answer is not at this time. Whether it ever will is in question. But it was on my list of things I wanted in the XP-8. Maybe it will be something that they can add later. But for now... nope.