It depends on the VPS; you'll have to try assigning addresses from this block to your VPS and see if they ping. In other words, check if you can reach your specific VPS using these IP addresses.
I'd suggest doing a trial purchase for a short period to test it out. Everything will depend on the provider. If the provider routes the entire block to your VPS correctly (and doesn’t block anything), then you'll actually get these 2^64 IPs to use. But whether you can effectively use them as, say, proxies is another story. Because sites like Google might just treat the whole block as a single IP, given they're already familiar with the provider's architecture.