In fact the .ttc file is a "true type font collection" ; it can be broken up using
breakttc, and using this I generated a valid .ttf file.
The attached font-text ebook show up the Cambria font, and I'm pretty sure it works : I uploaded it to my 505, and judging by the 'y' and 'j' letter shapes I think it shows up the proper font.
Hope this helps,
David.