My understanding of La Sangrada Familia is that it is an expiatory temple, build for the atonement of the people of the world, and is not a 'church' in the modern sense. There has been no formal worship service in it at any time, and may likely never be. It is not of any denomination, but is of all faiths.
Two excellent novels, both in English, Gaudi Key (translated from Spanish this summer [La Cave Gaudi, Spanish]) and The Shadow of The Wind, touch on this aspect of the temple. Sorry, I do not have the names of the authors handy. Both books incorporate the meanings of the symbols in Gaudi's work, and while fiction, offer good insights to the work.
A college professor told me last year of the completion date - and that the funds for the completion were to come from Japan.
At any rate, it is certainly an impressive and imposing structure. I hope to see it again!!
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Silver Traveler