From
http://www.oneworld.com/ffp/lounge-access/:
Customers flying in Economy class on the domestic or intra-European segment to connect to or from a oneworld longhaul First or Business Class flight can also use the lounge applicable to the class in which they are travelling the longhaul segment.
You are definately entitled to access the lounge in BER (print a copy of this rule from OW website to be safe). However, VCE might be a bit more difficult, as you are not connecting to a longhaul flight directly, AB has no lounge in VCE, and the lounges other OW carriers used are operated by 3rd parties. BTW, who is the "OW" agent you are referring to? There really is not such person to be the "OW agent."