Maxon just announced the availability of a new free plugin to export comps from After Effects (CS5 or CS5.5) directly to a .c4d file. There were some scripts that previously existed to get some 3D data out of After Effects. However, this plugin looks to be much more robust. According to the press release:

The CINEMA 4D export appears directly in the After Effects export menu and generates a .c4d file containing 3D layers, cameras, lights, solids, nulls and footage. Even nested compositions are supported. All major layer attributes including animations (rotation, position, parameter, anchor points, POI, etc.), expressions, layer parenting, layer locking and layer visibility are retained. Render and document settings in CINEMA 4D are adapted accordingly to the After Effects’ project settings.

We haven’t had a chance to thoroughly test this yet. But when we do, we’ll post the workflow, any potential pitfalls, and workarounds necessary. The plugin is free, so go grab it now!