So are the frozen chests tradeable or not?

All of these recipes can be vendored for various values, so that once the event is over can sell them for gold. From Jan 6 to Jan 13 the crafting recipes for the event Gems and combining chests will still be valid to craft. In a patch on Jan 13th these recipes will be removed and no longer able to be combined. The recipe item left in your inventory will be able to be sold for gold.
And then a contradictory:

In order to provide access to the event for all level of players, Bronze, Silver, Gold, and Imbued Frozen Chests are NOT tradeable and NOT stashable. This is to prevent an exploitable situation where players can farm for higher quality chests at lower levels to sell to other players, or move to their own higher level players.