Being this is the first time the series is to commence with a two-part story, the second episode Day of the Moon has also been subject to intense speculation as to whether it too would be shown over the Easter period. An intriguing piece of information has emerged via the CV of actor Jeff Mash; as well as being cited as playing a character called Grant in the episode, the CV also includes an entry that states that episode two will be broadcast on 24th April.
This entry certainly lends credence to the suggestions that both parts would be shown over Easter!
However, at this time the BBC have only confirmed via the end of the Red Nose Day special that The Impossible Astronaut will see its premier on BBC1(HD) over Easter 2011.
Schedules are generally not 'locked' until around a fortnight before broadcast, so any information published via the Internet prior to then may not accurately reflect how the show will eventually be broadcast.