When do constructors of static members of template classes get called in C++?

There is plenty of information on when constructors of static members of ordinary classes are called. However, I am seeing some strange behavior with regard to template classes.

What should the output of the following program be? (Note I use printf to avoid any static initialization order fiasco complications with std::cout.)

#include <iostream>

class B {
public:
  B(const std::string &s) { printf("Hello I am B from %s\n", s.c_str()); }
};

template<typename T>
class Atempl {
public:
  static B b_;
};

class A {
public:
  static B b_;
};

template<typename T>
B Atempl<T>::b_("Atempl");
B A::b_("A");

class C : public Atempl<int> {
};

int main(int argc, const char *argv[]) {
  return 0;
}

I think the output should be:

Hello I am B from A
Hello I am B from Atempl

But with g++ 4.3 on FreeBSD 7.3 I get:

Hello I am B from A

If I add the line

template class Atempl<int>;

all is well and I get the expected output. The question is, why doesn't the declaration of class C count as an instantiation of the template Atempl and cause B's constructor to be called? Is this part of the standard or a bug in g++ 4.3?