motion blur with moving camera also on 2d layers?

motion blur with moving camera also on 2d layers?

i wondered if it is possible when you have an animated camera to have motion blur on 2d layers. my setup is the following. after 3d tracking a video and modelling i rendered the 3d camera with different layers (shadow, highlight ...) to get them composited over the video again in after effects. this works fine, but to save some time i thought i will render the motion blur in after effects. so i imported the camerapath into after effects and turned on the motion blur buttons (for the comp and the layer). but i figured out that only static objects in 3d space get the motion blur. layers which are still 2d are not affected. the thing is i can't transfer my compositing into 3d as the position will get screwed up. also with auto orienting towards camera i am not able to get the right position.
is there a way to solve this problem to get the motion blur maybe with an expression onto the 2d layer?

thanks in advance
jakob