255.2. When an immovable referred to in a provision under section 255 is included in a non-taxable unit of assessment and belongs to several owners, not all of whom are persons referred to in that provision, the second or third paragraph of section 255.1, as the case may be, applies as if the immovable consisted only of that part attributable to the owner or owners referred to in that provision.
The provisions of section 255 under which the amount provided for in the first paragraph of section 254 is computed in the same way make up a group. The first paragraph does not apply if all the owners of the immovable are referred to in provisions that are part of a same group. If several of the owners but not all of them are referred to in provisions that are part of a same group, the parts of the immovable attributable to them are grouped together and constitute the part referred to in the first paragraph.