BA94 was Speedbird Niner Four up until mid 2008 when it was changed to 8YG. BA95 flew as Speedbird 7MY (iirc) for a while around the same time but was changed back to Speedbird Niner Fife.
Probably to do with BA294 as Thunderbug / bigjames mentioned, the change was probably caused by one of the flights being retimed or someone complaining.
I wish the people I work for would get into the alphanumerics. Picture 6331, 6321, 5231 and 1339 (to take just one example) all on frequency at the same time, late in the evening with thunderstorms doing their best to obscure the radio.
S.