I see it as pretty simple as working with a solicitor on alot of rfp type dealings some people since it is regulated to have a physical address choose to use a non traditional ways to receive incoming mail. Some administrative entities who do no bussiness face to face want to remain and keep a sense of privacy. Alot of companies use po boxes. I am not saying it is or isnt shady but if the asset is owned or rented by the company I wouldnt care. Run an address check and see if it comes back to them.