Of course. It uses the Text [0] and Scientific [1] packages under the hood. The internal ADT representing JSON is actually very simple (as json is very simple itself):

  data Value
    = Object (HashMap Text Value)
    | Array (Vector Value)
    | String Text
    | Number Scientific
    | Bool Bool
    | Null

[0] http://hackage.haskell.org/package/text-1.2.3.1/docs/Data-Te...

[1] http://hackage.haskell.org/package/scientific-0.3.6.2/docs/D...