Full letter here. First word is that the restrictions of 1988 forbidding interaction with the government-run Church are lifted. Interesting.
With a few paragraphs for context, and urging you to read the entire letter for full context, the passage below, especially the last paragraph, seems to speak not only to this but to other situations:
Moreover, faced with certain problems that have emerged in various diocesan communities during recent years, I feel it incumbent upon me to recall the canonical norm according to which every cleric must be incardinated in a particular Church or in an Institute of consecrated life and must exercise his own ministry in communion with the diocesan Bishop. Only for good reasons may a cleric exercise his ministry in another diocese, but always with the prior agreement of the two diocesan Bishops, that is, the Ordinary of the particular Church in which he is incardinated and the Ordinary of the particular Church for whose service he is destined.47
In not a few situations, then, you have faced the problem of concelebration of the Eucharist. In this regard, I remind you that this presupposes, as conditions, profession of the same faith and hierarchical communion with the Pope and with the universal Church. Therefore it is licit to concelebrate with Bishops and with priests who are in communion with the Pope, even if they are recognized by the civil authorities and maintain a relationship with entities desired by the State and extraneous to the structure of the Church, provided – as was said earlier (cf. section 7 above, paragraph 8) – that this recognition and this relationship do not entail the denial of unrenounceable principles of the faith and of ecclesiastical communion.
The lay faithful too, who are animated by a sincere love for Christ and for the Church, must not hesitate to participate in the Eucharist celebrated by Bishops and by priests who are in full communion with the Successor of Peter and are recognized by the civil authorities. The same applies for all the other sacraments.
Concerning Bishops whose consecrations took place without the pontifical mandate yet respecting the Catholic rite of episcopal ordination, the resulting problems must always be resolved in the light of the principles of Catholic doctrine. Their ordination – as I have already said (cf. section 8 above, paragraph 12) – is illegitimate but valid, just as priestly ordinations conferred by them are valid, and sacraments administered by such Bishops and priests are likewise valid. Therefore the faithful, taking this into account, where the eucharistic celebration and the other sacraments are concerned, must, within the limits of the possible, seek Bishops and priests who are in communion with the Pope: nevertheless, where this cannot be achieved without grave inconvenience, they may, for the sake of their spiritual good, turn also to those who are not in communion with the Pope.