Romans 11:28-29
"In respect to the gospel, they [the Jews] are enemies on your account; but in respect to election, they are beloved because of the patriarchs. For the gifts and the call of God are irrevocable."
Because of this reference to the "patriarchs" I would say Evangelium Gaudium is referring to the Abrahamic covenant, not necessarily the Mosaic.
Always important to look at the actual words.
Yes, It is always important to look at words and not to parse them. And I find it quite interesting that you did not post the preceding sentence in your Romans’ quote:
[26] And so all Israel should be saved, as it is written: There shall come out of Sion, he that shall deliver, and shall turn away ungodliness from Jacob. [27] And this is to them my covenant: when I shall take away their sins.
More from Romans 11:
“[6] And if by grace, it is not now by works: otherwise grace is no more grace. [7] What then? That which Israel sought, he hath not obtained: but the election hath obtained it; and the rest have been blinded. [8] As it is written: God hath given them the spirit of insensibility; eyes that they should not see; and ears that they should not hear, until this present day. [9] And David saith: Let their table be made a snare, and a trap, and a stumbling block, and a recompense unto them. [10] Let their eyes be darkened, that they may not see: and bow down their back always.”