Ceiling grids come in three basic weights. If you find the heavy duty weight, it may be sufficient to attach the conduit to the grid. Light duty grid, never. Yes, it is required by the building code to obtain the permission of the engineer who designed the ceiling grid to attach the wiring to the grid. We lowly electricians never know the weight of the tiles, nor the capacity of the supporting wires, nor the weight of the grid.
Seems kinda odd, because the weight of the fixtures is often much greater than the weight of the wires, and there is no limit on the number or weight of fixtures in the NEC, other than the manufacturers installation instructions.
