That document can be found here:
Here is the conclusion of their study:
"The conclusion of this study is that there are theological and liturgical reasons to hope that infants who die without baptism may be saved and brought into eternal happiness, even if there is not an explicit teaching on this question found in Revelation. However, none of the considerations proposed in this text to motivate a new approach to the question may be used to negate the necessity of baptism, nor to delay the conferral of the sacrament. Rather, there are reasons to hope that God will save these infants precisely because it was not possible to do for them that what would have been most desirable— to baptize them in the faith of the Church and incorporate them visibly into the Body of Christ. "
One of the texts that this document cites in support of its claim is this:
"The Church believes that “the Holy Spirit offers to all the possibility of being made partners, in a way known to God, in the paschal mystery”"(Gaudium et Spes 22)
This text seems to say that every child who dies before baptism in some way have the opportunity of attaining eternal salvation. The only interpretation which would exclude this is if the text was only referring to adults. However, that seems contrary to the text, and there is no indication that this is what is meant.
Pius IX wrote in Quanto Conficiamur Moerore, "Because God knows, searches and clearly understands the minds, hearts, thoughts, and nature of all, his supreme kindness and clemency do not permit anyone at all who is not guilty of deliberate sin to suffer eternal punishments"
It is not clear why God's mercy would require that he not permit an adult who had not commited deliberate sin to to suffer eternal punishments, but not an infant. Hence it seems more reasonable to apply God's mercy in a universal way, so that to both adults and infants He offers the possibility of eternal salvation. This is also in accordance with the text from Gaudium et Spes.
If we consider the relation between infants in the Old Testament and those in the New, it seems rather strange that we would say that after the coming of Christ it became harder for infants to be saved. Before the coming of Christ, children of devout Jews were able to be saved through the faith of their parents, as St. Thomas says. Thus, while we cannot assert that the same thing holds true in the New Covenant, it would be strange that the condition for Baptism being a means for salvation is that God should limit his graces upon those children who are so unfortunate as not to receive it.
Cardinal Ratzinger writes something that seems to imply this:
"The question of what it means to say that baptism is necessary for salvation has become ever more hotly debated in modern times. The Second Vatican Council said on this point that men who are seeking for God and who are inwardly striving toward that which constitutes baptism will also receive salvation. That is to say that a seeking after God already represents an inward participation in baptism, in the Church, in Christ.
To that extent, the question concerning the necessity of baptism for salvation seems to have been answered, but the question about children who could not be baptized because they were aborted then presses upon us that much more urgently.
Earlier ages had devised a teaching that seems to me rather unenlightened. They said that baptism endows us, by means of sanctifying grace, with the capacity to gaze upon God. Now, certainly, the state of original sin, from which we are freed by baptism, consists in a lack of sanctifying grace. Children who die in this way are indeed without any personal sin, so they cannot be sent to hell, but, on the other hand, they lack sanctifying grace and thus the potential for beholding God that this bestows. They will simply enjoy a state of natural blessedness, in which they will be happy. This state people called limbo.
In the course of our century, that has gradually come to seem problematic to us. This was one way in which people sought to justify the necessity of baptizing infants as early as possible, but the solution is itself questionable. Finally, the Pope [John Paul II] made a decisive turn in the  encyclical Evangelium Vitae, a change already anticipated by the  Catechism of the Catholic Church, when he expressed the simple hope that God is powerful enough to draw to himself all those who were unable to receive the sacrament."(God and the World)