i think you have had your leg pulled by your mate

it wont start without ecu, the ecu controls almost everything on zetecs. from fuel pump, to starter, injectors, idle, etc

thus the easy to steal bit would be incorrect coz u would have to tow it but yes, the Passive Anti Theft system is integrated into the ECU so, in theory - if the car could actually start without ECU (which it wouldn't) it would be easier to steal.