if you take your beloved hybrid to your favorite service station - be prepared to divorce your wife as you will have no money left when you take it for repairs (If you can find a mechanic/dealership that will touch it) - the mechanicals are easy, the high current electrics are not.
they are only worth buying if you have a proper dealership that can service it properly. The job risks for the mechanics are high too.
anyway - a person in Karachi had a Prius which he converted to CNG, and the AWESOMELY STUPID CNG mechanic had a hard time rigging it but he did. So the drive cycle was
sit - push button, ready - Drive - 35 km/h engine start,,,, - convert to CNG - drive - stop. drive, engine start on petrol then convert to CNG. - his Prius had issues as the CNG engine could not produce enough torque to run MG1 in the transmission as the system was expecting - it went into "clumsy mode"...