Yipe! That sounds to me like an accident waiting to happen, for a variety of reasons:
1) PVC pipe is not very strong. Threading any pipe greatly reduces its strength, especially in tension.
2) Screws into the narrow dimension of 1x4 can't be very large, or else they'll split the wood. I'm not a huge fan of screws used in tension for rigging anyway, as they can pull out, or loosen easily.
3) The T-Bar frame for a drop ceiling is not considered structural. It is NOT designed to support any weight beyond the weight of the ceiling tile, and while some loudspeakers and cable are supported by the frame, they do not represent any more of a load than thicker ceiling tile would. They certainly don't represent a point load of in excess of 10 pounds.
4) Not to mention he fact that untreated wood above a false ceiling may or may not be kosher with the building inspector, ditto on the PVC pipe.
I would be EXTREMELY hesitant about suspending an expensive projector using the method you describe.
Most projector installs I have seen either run steel pipe from the structural ceiling above the false ceiling to the projector mount, using appropriate fasteners at the top, or run threaded rod from the structural ceiling to a steel plate above the ceiling, to which the mount is attached.
Cutting corners on rigging to save a few dollars is not a wise business decision. If a projector were to fall, and a lawsuit were to be filed against the installer, the costs of the lawsuit would far outstrip any cost savings gained by cutting corners. Rigging is one place where you can't afford to cut corners.