I have spent a fair amount of time searching through the usual archives and repo databases, but most links I've found are either dead, corrupted, or actually lead to the later 256KB "Complex" or "Xecuter" BIOS files rather than the raw Mcpx dump.
The binary is not encrypted. It is plain ARM machine code, though small. Disassembling it reveals a very short, deterministic bootstrapper. There are no Microsoft copyright strings or logos inside—it is literally just the minimal code to wake the system. Mcpx-1.0.bin Bios