iana.org (Internet Assigned Numbers Authority) is the global organization governs IP allocations worldwide. And it has regional sub bodies to govern respective area such as:
AFRINIC Africa Region
APNIC Asia/Pacific Region
ARIN Canada, USA, and some Caribbean Islands
LACNIC Latin America and some Caribbean Islands
RIPE NCC Europe, the Middle East, and Central Asia
These organizations allocate IPs for the ISPs on respective regions and ISPs allocating IPs to their customers. ISPs must update the respective regional registries with customer details for IP allocations.
Each of these sub bodies have an online tool (Whois) where we can check these IP allocations. For example, APNIC has a site http://wq.apnic.net/static/search.html where we can check who owns IP address.
Hence in your case Company B can verify the relevant IPs on respective regional registry’s Whois site.
Note: This only works if the enterprises/organization has been allocated dedicated IPs for their usage by IANA or their ISP.