[Keith]

Funny enough the presser from the BBC states "The five chief presenters announced today were recruited via a competitive interview process in accordance with BBC HR procedures."...

I imagine they probably were, if only for the purposes of avoiding/minimising the chances of any claims of unfair dismissal.

Additionally, by making existing presenters apply for the few remaining roles it does potentially allow the BBC to issue new employment contracts. In general this coincidentally often results in a change (i.e reduction) in salary and/or change (usually removal) of other benefits and conditions.