Alrighty, it looks as though there are two versions of the c100 series as well - one with a regular NAND flash interface and one like the v3 m200s and e200/c200 v1s with the bonus chip acting as an SD interface.
Yes, the presence of that SanDisk 'SDC1' chip on the C150 strongly suggests it's using the same architecture as 'HARP'-type M200s (hence why you can't read the NAND Ids directly).
AIUI you'll need an SD-card driver to be able to read/write the internal flash on that device (as per the E200s and C200s). You could talk to preglow, he's been working on an SD driver for TCC78x which should be pretty similar.