can a timing belt replacement cause a main or rod bearing to fail ?

SHOULDN'T BUT DEPENDS ON ALOT OF CONDITIONS.SEAT AN INSP FROM ANOTHER SHOP AND GET THERE OPINION

No it cant. The timing belt runs on the cam gears and the crankshaft sprocket. There is a automatic tensioner to keep the tension at a certain rate. Theres also a water pump and a idler pulley. Nothing with a timing belt change can do what your asking on this car.

No But improperly installed can cause valve damage, depending on the rpms achieved while cranking and if the dual overhead cams were not aligned properly during installation. All 3, the crank gear and both timing gears need to be aligned with marks and if not will definitely sound like major rod or main bearing damage or a seized engine. If your lucky and no valve damage has occurred you can set these 3 marks, replace the belt, set the tension(be careful with this part) and possibly be back in action, Good Luck