As I am not a member of any church that has declared "impaired communion," nor have I seen definition of the term, I can only guess. But this is what it looks like to me:
1. Tanzania has declared that they are not in communion with various bishops (etc.) in TEC. Not at all.
2. Tanzania has expressed support for and desire for (continued) communion with certain elements within TEC.
Inferred: Tanzania does not want to declare that they are out of communion with *all* of TEC, because of the elements in #2. Therefore "impaired communion" does not mean "we are in a degraded state of communion with all of you" -- it means "we wish to preserve communion with some of you but not all of you."
That's this Anglican engineer's reading of "impaired", anyway. Maybe a lawyer could do better...
Then again, this raises the question you've noted before of communion with some in a larger organization that's 'out' -- but I think you're trying to see an endpoint in what are the middle of some Entish-Anglican processes. It may be that "impaired" can be defined as a preliminary warning.
"Inferred: Tanzania does not want to declare that they are out of communion with *all* of TEC, because of the elements in #2. Therefore "impaired communion" does not mean "we are in a degraded state of communion with all of you" -- it means "we wish to preserve communion with some of you but not all of you."
You know, in a sense and at a very, very basic level, this is Orthodox. Orthodoxy teaches that the fullness of The Church is found in an individual diocese and that any structure beyond that is really administrative. The glue which holds The Church, in a global sense, is the communion among its bishops in various dioceses. That communion in a theological sense is horizontal while in a purely administrative sense it is within a patriarchate or autonomous church both horizontal and vertical and among the patriarchates and autonomous churches similarly horizontal. In practice, the breaking of communion by one synod of bishops is not done with individual bishops but rather with the primate of the other church and by extension with the bishops of his synod who remain in communion with him. This is because one may not be in communion with those who are in communion with heretics. This system could even work in a slightly different way, for example when a member of a synod of a church falls into heresy, the primate of another sui juris church might insist that the primate of the former church break communion with the heretic. If that primate refused to do so, communion would be broken with that primate, etc.
I wonder if that is, in fact, what we are seeing here, or at least the beginning of that process?