Sadly there are very few members online at the moment. I did a few web searches but did not find any reference that either had memorized the bible. But it is obvious they have both studied it very well.
Having been a Christian in my younger days I can say that it would not be necessary for a Muslim to memorize the entire bible to be able to memorize enough key passages to present a very good refutation.
The major differences between Muslims and Christians are related to the Trinity, the divinity of Isa(as), and dietary restrictions. The Bible phrases referring to those things or lack of those things are all that need to be memorized to present a very good debate. It still is a significant feat to do so.