Digic 3 is capable of at close to that resolution, even on some P&S cams. Even the lowly TX1 was capable of 1280x720. However, even if the CPU/DSP is the identical for all Digic of a given generation (which isn't confirmed AFAIK), the CPU/DSP core is only part of the system. Buses, memory subsystems, IO subsystems all matter.
In any case, you wouldn't be able to just copy the video recording code from a different camera, and certainly not one with the major differences pointed out by DrMookenstein.