Don't concentrate on the IBM docs for their isolation stuff too much - it's mostly useless for the PS3. IBM uses its own isolation loader (which is stored in an OpenFirmware NVRAM variable on isolation enabled blades) and works hand in hand with their own userspace libraries and libspe2. The emulated isolation mode is just a unencrypted version of said isolation loader being loaded into a "normal" SPE. It's nothing the hardware explicitly supports.
Probably the only things that are equal between the IBM implementation and the Sony implementation is the basic setup to instruct the SPE to fetch the isolated binary from memory and enter isolation mode. From there on they're completely different.
Once metldr is running (see spuisolation.tgz floating around somewhere here in the forum) you have to figure out how to communicate with metldr. This could happen via the mailbox of the isolated SPE or via the small LS window that remains accessible even in isolated mode. The easiest thing to try would be to load one of the loaders (lv1ldr, lv2ldr, appldr) into memory and try to pass that address to metldr. Take care to align your binaries to 16 byte boundaries in memory or else the DMA will fail.
Just speculation, though.