The compression method is stored as an ordinal in the file so no real easy way to tell how the file is encoded. OpenEXR does support lossless and lossy compression. Whom ever posts to ILM's mailing list says they use 16bpc stored in the PIZ format internally. That is a lossless...
Does anyone know who is doing the manufacturing for nintendo? If it is ibm they may not know what speed chips they will be getting a la apple and they could have decided to keep quiet until the situation firms up.