Now I know the Ford Ka uses the 1242cc engine from Fiat. Does this engine also go in the Fiesta? There seems to be little written about the origin of the Fiesta engine.
The 1.2L Fiat FIRE engine used in the Ka is not used in the new Fiesta. Ford stuck to the 1.25L Zetec for the small engined variants (no doubt using whatever engine name they think is fashionable this year).
Coincidence. The bore and stroke of both engines is different (Fiat 70.8mm x 78.9mm, Ford 71.9mm x 76.5mm) but they just happen to work out to ~1242cc in both cases.