Are Muslims allowed to attend the Sufi's places and ceremonies in Khaneghah?

Fatwa, posted 4.22.2010, from Iran, in:
Religious Authority: 
Muhammad Taghi Bahjat
Fatwa Question or Essay Title: 
Are Muslims allowed to attend the Sufi's places and ceremonies in Khaneghah?

No, it is not allowed.

["Khaneghah" or "Khaneh-gah", literally means the "House of Present Time."
"Gah" is that real or true moment in which a person is present in the fullness of existence. It is said that the Salek (spiritual seeker) to gain spiritual knowledge needs to put aside social rank and seek to discover knowledge beyond the boundaries of time and space through the guidance of a spiritual master and practices of remembrance and invocation of God. The place in which such practices are taught is called "Khaneghah."]

محافل صوفيه شركت مؤمنين در محافل و مجالس صوفيه و انجام و اذكار آن‏ها و نيز حضور در خانقاه‏هاى آنان چه حكمى دارد؟ ج. جايز نيست.