Can you actually hatch a Pichu with the Ash hat?

I saw on Reddit that someone hatched a Pichu with an Ash hat during the one year anniversary event. In previous hat events, Pichu couldn't hatch with a hat.

Someone in the Reddit claimed they hatched an egg they received during the event and didn't get a Pichu with a hat:

Got an egg during the event and hatched it last night for a Pichu without a hat.

Is it possible to hatch one with a hat and if so, is it guaranteed to have a hat during the event or random?

YES, you can.

I hatched one this morning from a 2k egg, which I believe I got yesterday (i.e. after the "event" began). I've taken a screenshot, with the pichu at an angle for authenticity. ;)

I didn't realize it was possible, as the previous two hatted pikachus came before the baby pokemon were added.

Not sure if you have a definite chance of getting one with a hat or not, unfortunately.

Not sure if it's guaranteed, but the first two 2km eggs I've hatched since the event started (and picked up since then too) were Ash Hat Pichu's.