I'm sorry, but this looks like a major " How easy would you catch me if I...? " moment.
Either way, I know how it works. The Mod just simply looks at the account, and clicks the button.
Then it will show if there are any accounts with the same IP.
Lots of mods such as trachy randomly click around all the time just to patrol.
As for Pokemaster, I would assume it's the same way. Although it could also be possible for him to have a full scan in his admin panel that locates any doubles.
The italics mark that that part isn't facts, just an assumption.
And it's only for people with DB accounts.