For toy RC transmitters, the answer is likely "no" unless you can find a transmitter or receiver pair that lets you re-flash the firmware of both ends, and have the tools to develop such firmware.
A much easier way to do this is to use Xbee radio modules. You can set them up to pair such that each end only talks to the given module on the other end. Then use an Arduino or similar on each side to read joystick inputs (transmitting side) and generate servo pulses (receiving side.) Or, if you're driving motor controllers, just drive them directly with serial commands, rather than RC pulses.