From the Watchtower Organization's own "Reasoning From the Scriptures":
"As a basis for translating the Hebrew Scriptures, the text of Rudolf Kittel's 'Biblia Hebraica' editions of 1951-1955, was used. The 1984 revision of the New World Translation benefited from updating in harmony with the 'Biblia Stuttgartensia' of 1977. Additionally, the Dead Sea Scrolls and numerous early translations into other languages were consulted. For the Christian Greek Scriptures, the master Greek text of 1881 as prepared by Westcott and Hort was used primarily, but several other master texts were consulted as well as numberous early versions in other languages."
So they used multiple sources in order to refine their translation to where they wanted it. Regarding the translators (also from "Reasoning From the Scriptures"):
"When presenting as a gift the publishing rights to their translation, the New World Bible Translation Committee requested that its members remain anonymous. The Watch Tower Bible and Tract Society of Pennsylvania has honored their request. The translators were not seeking prominence for themselves but only to honor the Divine Author of the Holy Scriptures."
Since the translators are anonymous, we cannot state whether it is a scholarly translation.
"It is an accurate, largely literal translation from the original languages. It is not a loose paraphrase, in which the translators leave out details that they consider unimportant and add ideas that they believe will be helpful."
Now this is the quote from the same book that all Jehovah's Witnesses have when they go door to door. I'd like to rebut the above quote -- The New Testament translation in the New World Translation has taken out the Greek words 'Theos' (God) and 'Kurios' (Lord) in over 60 places within the NT and replaced them with 'Jehovah'. Jehovah occurs nowhere in the Greek, in fact the word was only popularized in the 18th-19th century. It's extremely important to understand this point when considering if the NWT is 'true' to the original language.