I don't know how likely other accelerators are to have found the Higgs-Boson, but the article at least makes an attempt to back up its claim:

"Lower energy levels have been accessible to smaller accelerators, such as the Tevatron at Fermilab and the LEP—the LHC’s predecessor at CERN—and neither collider had found it. Perhaps the Higgs does not exist at all."

Neither collider has enough data in those mass ranges to give any useful result. That's WHY the LHC got built.

What about the >466 GeV range? Is that considered a possibility? Can the LHC explore that high?

See http://resonaances.blogspot.com/2011/08/higgs-wont-come-out-... for discussion. Basically, it's possible, but requires physics beyond the Standard Model.