Currently the spec says:

[[
Any value of this id attribute MUST be unique either among all <locQualityIssues> and
<provenanceRecords> elements within the given enclosing <unit> element if the ITS Module
elements, on which the attributes are set are children of a <unit> element, within the enclosing
<group> element, in case of <provenanceRecords> elements that are children of a <group>
element, or within the enclosing <file> element, in case of <provenanceRecords> elements
that are children of a <file> element.
]]

But the value probably need to be unique at the document level to match the ITS semantics.
A pure ITS processor would not be able to make the distinction of scope done by XLIFF.