Short answer, episcopal conferences have no authority, including doctrinal, unless a decision is approved unanimously by all member bishops or if the Apostolic See specifically grants it authority (under current law, a 2/3 vote of a plenary assembly, together with a recognitio of the Apostolic See, is required for an authoritative decision). The various committees and offices have zero authority.
At the end of the day, in accordance with the divine law, each bishop is subject to the supreme authority of the Church, but otherwise sovereign. In fact, the Church forbids them from limiting their own power in favor of the conferences.
See here for a more in depth explanation on such conferences:
http://www.vatican.va/content/john-...-ii_motu-proprio_22071998_apostolos-suos.html
In general, when it comes to Church authority in political matters, the following apply (from the Catechism):
2245 The Church, because of her commission and competence, is not to be confused in any way with the political community. She is both the sign and the safeguard of the transcendent character of the human person. "The Church respects and encourages the political freedom and responsibility of the citizen."52
2246 It is a part of the Church’s mission "to pass moral judgments even in matters related to politics, whenever the fundamental rights of man or the salvation of souls requires it. The means, the only means, she may use are those which are in accord with the Gospel and the welfare of all men according to the diversity of times and circumstances."53
We should certainly respect the moral judgments of bishops by virtue of their divinely constituted offices, but when it comes to applying them to particular circumstances or when it comes to determining what is best for the common good among multiple morally acceptable options, they are not omniscient and one can certainly disagree in good faith.
As the Catechism notes above, “The Church respects and encourages the political freedom and responsibility of the citizen.”
