Not sure about Elm, but there are businesses using Microsoft's Reactive Extensions. I know Netflix had a series of blog posts on their use of RxJava and I believe they use RxJS as well.
If he did say that, I'm not sure Evan still takes that position. At least the last time I saw him talk about it (at SPLASH), he didn't put Rx in the FRP bucket. I know Erik (the creator of Rx) definitely wouldn't put Rx in the FRP bucket. And Conal (the creator of FRP along with Hudak) would only begrudgingly except Elm as FRP.