Problem: There is two bricks with common surface. 1) It's needed to mesh one by prism elements (based on one free brick's surface). OK! 2) Than transfer the prism elements to tetrahedral elements. OK! 3) Than mesh second one surfaces based on the surface mesh getting from prism element creation along with unchanging of first brick mesh. PROBLEM!

Do you want two volumes, one with structured mesh & another with unstructured and have a continuity between them (Same nodes at common surface)?

Yes of course! I've spent a lot of time and didn't get the good result. To clarify I can send the project files. I think it's really ICEM's bug and will be interesting to consider.