I think one of the reasons Bjorn Again hit the headlines is they very cleverly released an EP of Erasure covers as they would have been if Abba had recorded them. Got them into the charts.
1988 seems to have been a big year for tribute acts - I thought Australian Pink Floyd may have pre-dated BA, but they were both around the same time. Then there's Rutles of course, way earlier, and a Stones tribute who used to feature on Steve Wright's Radio 1 show.