Ynys Mon (Anglesey) Council today decided to make Welsh it's sole administrative language. The council came under Plaid Cymru control earlier this year.
Council to make Welsh its first language ... but struggles to recruit bilingual staff - Daily Post
It thus brings itelf into line with Gwynedd Council which is situated on the other side of the Menai. Gwynedd has followed the policy since it's creation in it's current form three decades ago - & there have been few if any problems.
Now it's unlikely that any Irish county could make Irish it's only administrative language - but could Donegal or Galway move in that direction & make far greater use of it in it's administration?