[left of center]

The signage/naming rights could have been bought by CNA, or given to them as a incentive to move into or remain in the building at some point when they were tenants. If it was the former, then the naming rights would continue until the contract is up, since the rights are bought and paid for. If its the latter, then the building owners can take down the signage and have it replaced at any time once CNA moves out.