I can't add to who this is, but I can say they're going to be difficult to find.
I Use Voicenetwork.ca for my IP phone service, my phone number is 305.890.XXXX -- seeing that it's so close to the above, it may be through the same company, or it may be simply a faked callerid number.
305 is Miami Beach - that's where I'm at, but I also have a Chicago number for that matter. This one caught my interest since I rarely see another 305.890 here in Miami.
Hope that can help to some degree, although in reality it probably makes the annoying [***] harder to track down; if the return call can't be made to them it's likely a faked callerid or a line that can only be used for outbound, a true [***] to get away from. Especially since it sounds like they're gaining nothing, only harassing people.