Years ago, Blanchard was briefly teamed up with Valeria Vorobieva, but nothing ever came of the partnership. Another pairing with Rinata Araslanova also aborted in the early stages. In both cases, there seemed to be a problem with one country to release the skater to skate for the other country.
Blanchard is now 28 and will turn 29 in July, and hasn't skated competitively in years.
I'd be shocked if this pairing is successful.
As for eligibility to skate internationally, there should be no problem since Blanchard has been away from competition for so many years. They can compete in the GP, but can get an original invitation only as a host pick. They can be on the alternate list to fill any vacancies due to withdrawals, as well.
For Volosozhar/Trankov, they must wait to compete until a year has passed since Tatiana skated for Ukraine. V/M last skated competitively at Europeans 2010, 1/19-1/24. This season, Europeans will be held 1/24-30, so it may even be technically possible for V/T to skate at 2011 Europeans. But they cannot compete in the GP this season.