Does anyone think that "gets filled" should also be accepted? NOTE: If the English version with "is filled" is given to be translated into Irish (or other language) it is potentially ambiguous since it could refer to an action that gets done to the bottle, as in this example, or the resultant state (ie it has been filled and is now full).
Exactly. The Irish autonomous (“passive”) form always specifically refers to an action, not a state. In fact, the best translation of this sentence would be “Someone fills the bottle with wine”. Of course, “is filled” is just fine as well, but so is “gets filled”, which should be accepted as well.
How would "with water" be written? "Líontar an buidéal le t-uisce"? Or "le uisce"?
le huisce. However, it's worth noting that the <h> isn't pronounced in parts of Connemara.
Shouldn't the bottle fills with wine also be accepted? It has the same meaning as the accepted answer.
No; the autonomous verb precludes that meaning. It could be translated as “One fills the bottle with wine”, though.
Because líontar refers to the action of an unnamed subject filling the bottle, not the state of the bottle after that unnamed someone has filled it.
In English, when you want to avoid mentioning the subject of a verb (the person doing the action), you use the passive voice. In Irish, you use the saorbhriathar.