The Cell is a family of processors, of which the one in the PS3 is just one of them. There is no reason that one that went into a TV would need to run at the same clock rate, or have the same number of SPUs or even have the same CPU architecture.
For example Toshiba have had the SpursEngine for 3 years now. It is a a coprocessor which has 4 SPUs, no CPU, some hardware accelerated H264 / MPEG-2 circuitry and ran at 1.5Ghz. The idea was you stuck it on a board of laptop, or in a TV and called it from the main processor which could be x86, ARM or whatever.
Maybe CEVO is just a further refinement, integrating a low power CPU and rejigging the SPUs making it more suitable for TV devices and so on.