Eric Lawee, Isaac Abarbanel's Stance Toward Tradition: Defense, Dissent, and Dialogue, p. 39:
No less novel and pronounced than his interest in history and politics were Abarbanel's broad knowledge of, and ecumenical attitude towards, Christian exegetical literature. Thus, the discussion of kingship in the commentary on Samuel paid special heed to teachings of the prominent fourteenth-century converso churchman, Paul of Burgos. Elsewhere, within a dozen pages Abarbanel found occasion to refer to the Vulgate, praise as "very fine" an interpretation advanced by unnamed Christian commentators, reject without disparagement another Christian interpretation, and, while arguing contra Maimonides, invoke with approval prophetological views of Christian theologians. In treating the enigmatic story of the witch of Endor, he adduced the "greatest of the Christian scholars Augustine" and offered an explanation of necromancy built on the premise that spirits do possess a certain manner of knowledge of future events--a premise confirmed in writings of "all the gentile scholars and adduced by the scholar Thomas in his work entitled Secunda secundae." One biblical interpreter with whom Abarbanel carried on a silent conversation was the supremely prolific mid-fifteenth-century Spanish Franciscan Alfonso de Madrigal, "el Tostado." It seems likely that it was in Iberia that Abarbanel first encountered and began to borrow liberally from Tostado's works...Three points here:
 [Commentary to] Samuel, 204-205.
 Ibid., 171, 181, 184.
1. The Abarbanel utilized and quoted Christian commentaries extensively.
2. He was somewhat unique in this regard.
3. I was told the following story by an eyewitness (retold in my own words):
During the debate over whether R. Emanuel Rackman would become the next president of Yeshiva University, R. Joseph B. Soloveitchik listed to a gathering of YU roshei yeshiva his reasons why R. Rackman was unfit for the position. Regarding one view of R. Rackman, R. Michel Katz objected that this view had already been stated by the Abarbanel. R. Soloveitchik responded that he wasn't so sure that he would want the Abarbanel to be the president of YU either.