Whether the lab made the inlay or onlay has no bearing on the code. It is the same as if you were billing for a crown made in a lab.

Depending on what type of material was used and how many surfaces covered would determine the code used:
Metallic onlay- D2542-D2544 or Metallic Inlay D2510-D2530
Porcelain/Ceramic onlay D2642 - D2644 or inlay D2610- D2630
Resin based onlay D2662-D2664 or inlay D2650-D2652