i'm pretty confident, but very rusty, that a description of a condition that presently exists but created in the past would be passive perfect in latin. i will admit to being far less skilled in english grammar.

ok i'm too far down this rabbit hole now but it's occurring to me that the question is whether this is a form of the word vacate or the use of 'vacant' as descriptor of the subject linked by 'were' i think

lol now let's do it what's confusing here is that often but not always a past participle is formed with an -ed form, and there are some irregular participles that look different parts of speech (was given, was shown, was done, etc).

We form the passive in English by combining a conjugation of the "to be" verb with a past participle: is done was killed will be exonerated etc.

That's in contrast to the perfect tenses, which indicate simply that an action has been completed. This can occur in past, perfect, or future tenses: he had done it he has done it he will have done it

Note that whether a tense is perfect is a different question from whether it's passive, and the two can be combined: it had been done already it has been recorded it will have been explained are all both perfect and passive.

But we don't want to conflate passive constructions with predications that share a root, e.g. "The bucket had been emptied" is a different thought than "The bucket had been empty."

So here, "the positions were vacated" (passive, past) "the positions had been vacated" (passive, past perfect) "the positions were vacant" (active, past) "the positions are vacant" (active, present) are all different thoughts and worth distinguishing

yup, you're right 'were vacated' creates the question of who vacated them (passive) were vacant is an active description of a past condition (active)