GDPR says no
Anything that can be connected with an individual falls under the remit of GDPR and can not be stored long term. There are exceptions, or correctly, workarounds that allow IP addresses to be stored temporarily for things like criminal investigation but, and this is a big one, only in connection with activity carried out on the network. So, a general appeal for data relating to a MAC address is in breach of GDPR of which the police should be aware. This could invalidate any case by making evidence inadmissible.