I heard myself, in person, Bishop Tissier de Mallerais, say with shock, that they had theological discussions with Rome for 2 years, and the preamble mentions not one word about it. That it simply says (my words) this is what we'll give you (Rome will give the SSPX) if you accept us as we are, Vatican II and all.
Three Bishops of the SSPX are against it, Bishop Fellay can't act alone, he does not own the SSPX properties, he can be removed as the Superior General. He can take people with him, priests and laity, but he can't take the properties. That said, I doubt he will do that. Don't be fooled, the SSPX bishops are very close.