It is counted if it is a QF flight number and point earning. While many BA flights have QF codeshares, they cannot be purchased without a longhaul sector.

You cannot transfer points or status between 2 programs within an alliance.

There are threads comparing the merits of the various one world programs in different situations.

If you don't have much at stake (low current status and not that many points), it may be better to consider all possible programs (not just one world) as to what suits your expected travel patterns.