So at present there are UK citizens residing in some EU countries who may not be permitted to vote in either Local or National Elections of the country they are residing in.
As far as I can see, POGS. But it was a very brief google..
So there is not a defined EU policy it has been at the discretion of each country.
So it appears, but, with regard to the EU v the UK offers on rights of EU and UK citizens, I believe (but this is hearsay as I haven't read either offer in detail) that the EU is offering (and asking for) the exactly the same rights as enjoyed at present by any EU citizen, in perpetuity, for those living in another EU country before the actual Brexit date whereas the UK 'offer' limits those rights for EU citizens in the uK, particularly with regard to voting (i.e they won't be able to vote in any election). But don't quote me on this...I may well be wrong...