I can tell you many stories of not only worshipping with other faiths, but of cooperation with other faiths here in Utah. One that comes to mind is a few years ago when the Catholic church didn't have enough room for all the Catholics who wanted to go to Midnight Mass on Christmas Eve. Somehow one of the LDS bishops heard about the dilemma, and got permission for them to hold Midnight Mass in the Provo Tabernacle (probably seats 2000). The mass was standing room only that night, I know because I was there. It was awe-inspiring to see two faiths in our community come together.
And no, the LDS church does not hold spiritual outreaches like Billy Graham does. But we do have General Conference twice a year. The Conference Center was built a few years ago, it holds about 21,000 people. Anyone can go, I'm sure we could find you a ticket, or you could stand in line waiting for the empty seats. There is no check at the door for religious affiliation. Plus, General Conference is broadcast not only in Utah over the local NBC affiliate KSL, but it is on radio, and many areas of the country either have it broadcast through their local TV stations, or broadcast it at their LDS meetinghouses. Again, anyone is more than welcome to listen in. They have even set up so that one can listen over the Internet. Many religious leaders of other faiths are invited to General Conference (they get the prime seats too, but I digress...:)