From that link:
Where did Luke get his stories about the conception, birth and infancy of Jesus Christ? Many believe this information came from none other than Mary, the Mother of God. Who but Mary could have told him the things that she kept in her heart? We know that Luke was with the Apostles at the same time as Mary. In aspiring to write an orderly account of the Savior's life and ministry, it would have been natural to ask Mary what happened from the beginning. It is therefore all but certain that she was a primary source for his account.
In other words, there's precisely zero evidence for anything. Quite cute circular logic, though.