Well he currently plays for Levski Sofia and has been in the country for a while already(the article says quite a lot). Im not sure if he speaks Bulgarian but I believe he does(probably some Levski fan, visiting this forum can say for sure). He was one of the decent players that helped Levski reach 1/4 finals on the UEFA cup. But no, he aint the first foreign born player playing for the NT. There were 3 Serbian born ones that played on Euro 2004 - 2 defenders and one attacking player(not sure if there was anyone else before them). The fiasco on the tournament naturally made many people blame the "foreigners". Whether thats true or not, no one can tell for sure but when Stoichkov replaced the previous manager, he promised not to call such type of players(though as seen now, he is good in the pointless talking).
I personally go against that not from any nationalist point of view(lol!) but because if the NT is screwed cauz,say, there isnt a good enough left back(the post where Vagner plays), well, just put whoever seems to be the least worse option. After all, those international games are about what football capabilities a country can pull out. If a country got screwed defence(the Bulgarian one is notorious for that), that should tell something about the youth facilities and not that there should be a recruitment spree from football-superior countries such as Serbia and Brazil.