Let's try analyzing it. Wikipedia offers the rule of thumb "commercial programmers write about 12,000 lines of code per year". That means there'd have to be around 400,000 active full-time COBOL programmers to write all that code.
From a random google search: "An estimated 1.5 million COBOL programmers are available worldwide. Payson has the names of more than 2,500 COBOL experts in his database alone." Sounds possible. From another: "There are 90,000 COBOL programmers in North America in 2002. Over the next four years there will be a 13% decrease in their number due to retirement and death." Sounds less so, although obviously that's just North America, but if 90K are in NA, are there really another 1.4M elsewhere?
From the same page: "15% of all new applications (5 billion lines) through 2005 will be in COBOL." Which makes me wonder whether the 5 billion number comes from somebody incorrectly combining two statistics: 33 billion LOC and 15%, where the 15% is a number from one source applying, say, only to commercial applications, and the 33Bloc is some other number (counting all scripting applications and etc).