From 1979 until, 1980, you basically found them in the "AA", "B", "D", "J", "LL", "M", "QB", "RR", "SS" (Franklin Ave. Shuttle), and occasionally on the "N".
After 1981, they were removed from the "AA", "B", and "D". Although you would still find them running on those lines very, very sporadically.
There was virtually no change from 1981 until 1987 when some of the R27s started appearing on the "C". The R27s also saw service on the "A" train for a short while during the overhauling of the R38s. Also, all R27s, R30s and R30As were removed from service on the "R" train after the May 1987 switch of the "N" and "R" northern terminals.
The bulk of the R27s remained on the "C" until they were retired from service in 1989. They were replaced on the "C" by the unrebuilt R30s (8412-8549?) (which began showing up on the "C" in the Fall of 1988) in 1989. During the spring and summer of 1989, rebuilt R30s (8250-8349) began appearing on the "C".
As of Fall of 1989, all R27s were retired from revenue service, all R30s (rebuilt and unrebuilt) were on the "C" and the rebuilt R30As (8350-8411) were on the "J", "L", "M", "Z" as well as the Southern Division "B" trains.
During December 1990, the unrebuilt R30s were removed from the "C" train and retired from revenue service. The R30A's were transfered from the "L" and "M" trains (they stopped operating on the "J" and "Z" circa Spring of 1990) replaced the unrebuilt R30s that were operating on the "C" train. This transfer also marked an end of an era of R27/30/30A's operating on the BMT, where they have been operating since they first went into service in 1960.
The rebuilt R30/R30A's remained in service exclusively on the "C" train until Summer of 1993 when they were retired from revenue service and replaced by R32s.