My sense of it is that if it is done out of love, and not trying to obligate the Creator to owe them salvation, then it is not a "work". As I have mentioned, Paul's definition of "work" is when we do anything that tries to obligate God to reward us. He rewards us because He is righteous, not because He owes us. Thus, when a Muslim does something out of love with no alterior motive, we presume that that it is the Spirit of the Lord who abides in that man (as no one can do anything good alone).
That is how I see the Church's teachings and the Scriptures.
Regards
If the Spirit of the Lord abides in a man he will leave Islam faster than you can say: "come out from among them"
And what concord hath Christ with Belial? or what part hath he that believeth with an infidel? And what agreement hath the temple of God with idols? for ye are the temple of the living God; as God hath said, I will dwell in them, and walk in them; and I will be their God, and they shall be my people. Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you, And will be a Father unto you, and ye shall be my sons and daughters, saith the Lord Almighty. (2Co 6:15-18 KJV)
That would mean that all the "good works" done by Atheists are accounted unto them as righteousness as they are not motivated by any desire to win brownie points from some diety.
So is the athiest's good works done out of selfless love buying him rewards in heaven? Is it accounted unto him as righteousness?