The 'Recently Deleted' feature is designed as the backup/recovery for inadvertently deleted photos. Once you delete them from there, though, that's kind of the death knell.
You: Delete these photos"
Mac: OK, but I'll hold on to them for a while, just in case...
You: NO, I'm sure. Delete them now
Mac: Are you really, really sure?
You: Yes! Delete them
...
You: oh... wait...!
That said, even though you delete the photos, they do still exist on Apple's servers - it can take several days between when you say to _actually delete the photos to when the raw data is deleted from disk in iCloud's servers. Unfortunately you have no access to this.
I'm guessing that with work (and likely a police subpoena) Apple could recover them still, but it's a lot of work and I've never heard of them doing it ad hoc (it's not a trivial process), but you could ask.
The other potential option is iPhone recovery apps - these scan the phone itself for deleted files and purport to be able to restore them. I have no specific recommendations about any of them, and can't vouch for their success rate, but there may just be a chance.
If you have Backups of your phone from before the photos were deleted, the software tools may be able to scan the backups to recover photos. No guarantees here, though, either.