[ELS]

I'm looking for documentation.

A few hits in Google for: celebret Tridentine "Ecclesia Dei"

6.Since a number of older and retired priests who have a deep appreciation of the previous Latin liturgical tradition have approached their individual ordinaries as well as this pontifical commission to obtain the celebret for the use of the 1962 missal

It will be noted that any priest requesting a celebret can be granted one without the agreement of his bishop. It is necessary only to inform the diocesan bishop that it has been done. It will also be noted that the 1962 Missal is mentioned specifically, as was the case in the motu proprio Ecclesia Dei.

They [sacristans at St. Peter's] are also requesting from all priests who wish to offer Mass according to the 1962 Missal to produce a celebret which is issued by the Ecclesia Dei Commission. While the Commission has the authority to issue celebrets without authorisation by a diocesan bishop, it has issued few if any since 1989.

[sinkspur]

Well, it appears that a priest may celebrate the Tridentine Mass with a celebret from the Commission. However, it still holds that a priest may not set up his own chapel, outside the jurisdiction of the bishop.

This exception is mainly for older priests to celebrate the Mass of 1962 in private.