They are bolted in place. Not that difficult to remove, but messy. The o/s one mounts the p/steer pipes and will fail the nct if rusted badly. These are very similar to the same brackets found on Fiat Bravo/Brava/Marea/145/146/147 etc. The top end where it bolts to the car is a different shape, but the bottom end (the bit that rusts) is the same. I've usually either fitted new ones, or rivit good bottom ends to the existing top end.
Unfortunatly, at this stage, Alfas of this era are beginning to show signs of rust.