plate ump covering 3rd

[ggk]

R1, base hit to the outfield, i believe the plate ump should cover R1 into 3rd while letting the base ump know same. does the same coverage apply on an infield ball where the runner may have been stealing and is trying to go 1st to third on an infield out or infield error? how about R2 only on an infield out - he waits until the ball is thrown to F3 and then breaks for 3rd. i think PBUC states that base ump has both infield calls, but why wouldn't the plate ump help out in those other situations?? thanks.