I've never heard of Roman Catholics having a "celebration of Evening prayer". We have Vespers at 6pm and Compline at 9pm. Whatever it is they are doing at 7:30, it is not Catholic. Not to mention they are having a snort and "fellowship" afterwards! Guess that is why Baptists were not invited, they shun alcohol under any circumstances.
You may be right.
However, the O.P. says that there's a Dominican priory and N.O. church. I have to wonder if it's a Dominican church attached to the priory. Dominican parishes are not usually under the local diocese, but they are their own entity, sort of. I attended a Dominican church for two years between the years I attended the Indult.
Also, the O.P. says that the prayers were after adoration. When I attended the N.O. Dominican church, they offered, several times a year, a "Mercy Night," of adoration, prayer, music and confession. Parishioners were encouraged to invite non-Catholics.
It could indeed be Anglican use, but it could also be Dominican.