The quote in the title is taken from paragraph 16 of the JOINT DECLARATION ON THE DOCTRINE OF JUSTIFICATION by the Lutheran World Federation and the Catholic Church. Is such a statement consistent or inconsistent with Reformed doctrine? If judged to be consistent, is it necessary to qualify the statement for it to fully harmonize with relevant doctrines?
This statement, by itself, is in line with the main strands of Reformed theology,1 when the word "call" is understood to mean external call.
The Scriptures, therefore, in the most explicit terms teach that the external call of the gospel is addressed to all men. (Charles Hodge, ST, 3.4.1)
[External calling] comes to both the just and the unjust, the elect and the reprobate. (Louis Berkhof, ST, 4.5)
the Reformed as a rule maintained the universal offer of grace. (Herman Bavinck, RD, 4.1.1)
Why the emphasis on external? Reformed theologians distinguish between an external and internal call. Berkhof explains the former:
The external call consists in the presentation and offering of salvation in Christ to sinners, together with an earnest exhortation to accept Christ by faith, in order to obtain the forgiveness of sins and life eternal.
On the other hand, the Reformed teach that the internal or effectual call is a work of the Holy Spirit through which a sinner is transformed and made able to come to faith.
So in short, the phrase "All people are called by God" is perfectly in line with Reformed theology so long as we understand "called" here to mean external calling, because the gospel is to be preached to all people. It could not mean internal calling, as that would indicate that all men are saved, which is universalism.
1 One of the distinctives of hypercalvinism, a minority view in Reformed theology, is that the call of the gospel goes only to the elect. For them, the statement in question would not be accurate. For additional information, including quotes, see What is the Calvinist and Hyper-Calvinist understanding of the “whosoever will” from Rev. 22:17?
A typical reformed response on this statement would be like that found in Matthew 22:14 “For many are invited, but few are chosen.”
A typical reformed expositor writes:
The gospel call goes forth far and wide. It reaches ever so many. Most of them are like the man in the parable: they hear but do not heed. In comparison with those many that are lost there are but few that are saved, that is, few that are chosen from eternity to inherit life everlasting. Salvation, then, in the final analysis, is not a human accomplishment but the gift of God’s sovereign grace. Cf. Luke 12:32; John 6:39, 44; Eph. 1:4. (NEW TESTAMENT COMMENTARY, WILLIAM HENDRIKSEN Exposition of the Gospel According to Matthew)
Regarding the article on Justification that is linked in your question, historical reformed teachers would most likely find it intellectually dishonest. The Protestant view of Justification occurs in a 'single moment' prior to any kind of moral ability to be had. A Catholic view of justification is that it is a life time process similar to what a Protestant calls sanctification. The article entirely glosses over this division, while grouping statements which both agree to under vary different senses. The Reformers would condemn this article and probably accuse the authors of deceit. The Reformers were not that interested in unity when it came to the central doctrine of the gospel which they believed the Catholic church to have utterly corrupted by denying the justification of a sinner 'in a moment' prior to sanctification.