Windows Server 2012 introduces dynamic assignment of virtual machine queues. If you do not have any traffic or very little traffic, you might see all queues assigned to one CPU ID. As traffic to the virtual machines increases, you should see the CPU ID assignment changing.
Another thing to keep in mind about dyanamic VMQ is that the logical cores created by Intel® Hyper-Threading Technology are not used for VMQ. Therefore, if you have 64 logical processors, you will only see VMQ using up to 32 processors.
Check out the section titled Dynamic VMQ in Performance Tuning Guidelines for Windows Server 2012.