Digital Ocean has something called "Private Networking" that's internal to the data center but shared with all other customers. It's not obvious from reading the website that this is the case.
If a user of the service is wanting to get on board, it is their responsibility to ensure what they think is accurate or not.
Any of these "datacenter LANs", though, tend to be fast and free (in terms of bandwidth). We just use a VPN overlay and call it a day.