To my knowledge, you just can't technically have hot-neutral loads in a delta system!
So if there's a neutral popping up somewhere, the only possibility is a wye without a neutral provided, which is legal in most European countries (no need to bond the neutral if it is a TT system, so if there are only symmetric loads you don't need a neutral, can omit it right from the transformer). I don't think adding a neutral from some other circuit to such a system would be legal.
On the other hand, in some countries it's legal to split up the yellow-green PEN far up in the system, so what looks like a ground might actually be a combined ground and neutral.
