The "T" pose isn't absolutely necessary! Some models are built with their arms at a 45 degree angle. I guess the logic there is that's where a character's arms are going to be most of the time!

You COULD probably rig and bind the character as is, but it might deform funny. It shouldn't be too much trouble to grab the existing geometry and rotate it up to a "T" or 45 degree position. I've done that a few times.

I agree, however, that posting the character would help. If it is someone else's intellectual property, you could post that along with the picture.