It is possible, although maybe not officially supported.
First read this for how to restore windows to a different machine. Restore windows server image backup from one server to another
Now for the tricks of getting it onsite to EC2. Likely easiest way is to restore it into a virtual machine on your site that is able to be Imported to EC2. Here's the details http://aws.amazon.com/ec2/vmimport/
The problem is it currently only supports Windows Server 2008 R2 and you said you're only at Server 2008. So the next option is to start new EC2 instance of Server 2008 and somehow use the Virtual Private Cloud feature to VPN back to your site to access the restore. Maybe an easier way would be to create a 2nd disk on the EC2 instance, copy your WindowsImageBackup directory to it over Remote Desktop, then try a restore from the EC2 machine.
If you get something to work please post a comment back on how you did it.