I wouldn't say it is impossible, but it strikes me as unlikely (Though do keep in mind that I am nothing but a guy with an above average interest in history; I'm mostly throwing out my thoughts here to have them vetted by those more knowledgeable than I!)

a) To listen to the radio, the German sub would've needed to keep an aerial above water; this would create a wake which could've been observed, with obvious consequences for the sub. I doubt a commander would have taken that risk.

b) I also doubt he'd risk surfacing near a foe armed to the teeth so shortly after cessation of hostilities - what if the battleship hadn't been notified yet? Or, just as bad - if they had, but assumed the sub hadn't been, and acted accordingly, just to be safe?

c) Further, in the last days of the war, Dönitz (head of the Kriegsmarine) ordered all vessels scuttled, rather than having them fall in enemy hands. I have no idea how many submarines were still operational and on patrol come V-E Day, but presumably most would have been scuttled or headed for South America by then.

So, while I find it unlikely, I wouldn't rule it out, and would love to know more about the incident.