Evidently in the coming weeks and months, we can expect some formal and official clarifications from the Ecclesia Dei commission on questions such as those about to follow, but there does seem to be a few misunderstandings brewing out there about the Motu Proprio that are worthwhile responding to now.
Obviously we make no claim to be the authoritative interpreter of these matters, but many of these issues seem to be reasonable to respond to by a simple, straightforward and contextualized reading of the document -- in other words, with the "lights" we presently have available to us.
To that end, we offer our interpretations of the answers to these questions with the understanding that we submit to the definitive judgement of the Holy See, the authentic interpreter, who will no doubt be approached about all these matters, given the confusion that is out there.
By putting these out there however, hopefully people will at least see fit to "reserve judgement" or "presume the best" until a definitive response from Ecclesia Dei (or otherwise) is made. However, I personally feel quite safe in the conclusions made for each of these questions.
Question 1: Does the Motu Proprio not allow the classical liturgical books of 1962 to be used for the Easter Triduum?
Response: The statement about what is not allowed during the Easter Triduum does not reference the 1962 liturgical books, but rather private Masses -- regardless of which liturgical books.
The classical Roman books are not excluded from the Easter Triduum. However, where and when they might be used during the Triduum will depend upon the pastoral circumstances. Certainly at 'personal parishes' that use almost exclusively the 1962 liturgical books, they will continue to use the 1962 liturgical books for the Easter Triduum.
Source Reference: "Art. 2. In Masses celebrated without the people, each Catholic priest of the Latin rite, whether secular or regular, may use the Roman Missal published by Bl. Pope John XXIII in 1962, or the Roman Missal promulgated by Pope Paul VI in 1970, and may do so on any day with the exception of the Easter Triduum."
Question 2: Does the Motu Proprio now allow the 3 year lectionary to be used that is employed in the missal of Paul VI?
Response: The Motu Proprio only mentions that in public masses according to the classical liturgical books, the readings may be in the vernacular "using editions recognized by the Holy See." It seems that this simply refers to the readings as found in the classical liturgical books and not the new lectionary.
The use of "edition" is likely causing the confusion (as well a rumour that came out prior to the MP release) but that would simply seem to be a reference to using a vernacular translation that the Holy See has approved for liturgical use. (e.g. an inclusive language translation may not be employed.)
An approved edition, it would seem to me, is much different than approving a different lectionary altogether -- one based upon a different liturgical calendar, with variations and differences in the liturgical seasons and Feast days.
The fact that it can be mentioned as an option that can be implemented in the here and now by priests at their own discretion would further point to the fact that it merely intends to formalize a practice/indult which allowed the use of vernacular form of the readings (as found in the 1962 Missal itself) to be proclaimed at their proper liturgical points. With the structural differences in the liturgical year, as well as the number of readings and so on, the challenge of incorporating such successfully and harmoniously would reasonably seem to require at least as much intervention, study and planning as the matter of introducing the new prefaces (which is to be studied by the Ecclesia Dei commission). It therefore seems highly unlikely that such was intended.
Source Reference: Art. 6. In Masses celebrated in the presence of the people in accordance with the Missal of Bl. John XXIII, the readings may be given in the vernacular, using editions recognised by the Apostolic See.
Question 3: The Motu Proprio does not mention the sacrament of Holy Orders. Are ordinations in the classical form therefore not allowed any longer?
Response: The Motu Proprio seems to be focused upon the sacraments that would be offered in parish life, and which apply to the discretion of the parish priest, or in the case of the Sacrament of Confirmation, which are offered by the Bishop in a parish setting.
The Sacrament of Holy Orders is specific to the Bishop and not inside a parish setting, which would be one possibility as to why it wasn't mentioned. It is also noteworthy that it is a current practice and one that is not specifically mentioned as being prohibited now. This is also relevant.
It would therefore seem that the present scenario will continue to apply: Ordinations in diocesan seminaries will occur in accordance with the modern form. Ordinations of priests studying in classical use seminaries will occur in the classical form.