Cities generally have to be at least partially in the telecom business, or there'd be five independent sets of telephone poles on every street.
Obviously there are a lot of details to be worked out, but are there any significant technical reasons this couldn't be done?
There's a lot of evidence that mandatory LLU reduces prices and increases speeds.
It's also relevant to note the background for LLU: the cables were almost all installed by a government owned telco, so there's a clear argument for the infrastructure being owned by the taxpayer. LLU came into existence as government telcos were privatised in the 90s to avoid creating a private monopoly.