ZTL Controller described an airspace incursion event indicating a standardized procedures should be adopted to preclude future similar type events.

Narrative

I was working the Rocket High Sector (R-06); the northwest arrival feeder to ATL. Arrival aircraft arrive on two streams; Memphis and Nashville. I issued an aircraft on the Nashville transition a pilot's discretion descent to FL240 and initiated a hand off to Sector 5 (DALAS). A B737 checked on my frequency climbing to FL310. I did not have a hand off on the aircraft nor had one been initiated from ZME. I figured the aircraft had been given my frequency in error. I pulled up the flight plan in URET to attempt to find the correct frequency for the aircraft. URET revealed that ZME Sector 60 had track control. When I examined the route; it appeared the aircraft would/should be entering my airspace at some point. The BNA..ATL.J45... aircraft are common and are worked by Rocket daily. It was odd that the aircraft was already climbing to FL310 as a BNA departure so I scanned to locate the limited Data Block. After moving a couple of Data Blocks; I saw the limited was directly underneath a second Air Carrier Y flight that had clearance to FL240. The limited Data Block was out of FL280 climbing quickly. I immediately turned Air Carrier Y southeast to avoid a conflict and attempted to track the B737. Shortly after; ZME Sector 62 called with a hand off. The aircraft was approximately 20 miles inside of my lateral boundary and 5;000 FT above the floor of my vertical boundary. Air Carrier Y had not left FL330 yet; otherwise separation would have been lost. Thank goodness for the pilot's discretion descent! Plans are in the works for BNA departures to climb to a fix that keeps the aircraft clear of the ATL arrivals. That would have prevented the possible loss of separation. The largest problem is that sometimes the BNA departures are climbed and handed off by ZME and other times they are left at FL230 and Rocket calls for a point out and climbs them appropriately. A standardized procedure would be beneficial.