4682 Legal status of a garage

We bought a house three years ago which had a zinc garage/box on the boundary. The garage was in the agent's details and also listed in the compromesso. However our suspicions were aroused (as to its legality) when it did not appear in the draft of the atto we had requested from the notaio. As the garage was essential for us we arranged with the agent and notaio to take advantage of a condono and the garage is now included in the atto, registered at the catasto and we are paying ICI on it. We therefore assumed it was now fully legal and 'safe' from criticism. We currently have the house up for sale but had we stayed long-term we thought we might be able to replace with a brick garage of the same dimensions.

So we were very concerned this week to meet the rightful owner of the land next door as she has said that she may require the garage to be demolished when she (hopefully) takes possession of the land in the near future. She seems to know the law quite well as she has been trying to get former tenants evicted over a 14 year period and appears to have been through the hierarchy of courts in the land

Is she right that it is still illegal due to its position on the boundary, despite the fact that it is registered?

Please can anyone assist with an opinion?