I think the exact terminology for what you need is “template covariance”, meaning that if B inherits from A, then somehow T<B> inherits from T<A>. This is not the case in C++, nor it is with Java and C# generics*.
There is a good reason to avoid template covariance: this will simply remove all type safety in the template class. Let me explain with the following example:
//Assume the following class hierarchy
class Fruit {...};
class Apple : public Fruit {...};
class Orange : public Fruit {...};
//Now I will use these types to instantiate a class template, namely std::vector
int main()
{
std::vector<Apple> apple_vec;
apple_vec.push_back(Apple()); //no problem here
//If templates were covariant, the following would be legal
std::vector<Fruit> & fruit_vec = apple_vec;
//push_back would expect a Fruit, so I could pass it an Orange
fruit_vec.push_back(Orange());
//Oh no! I just added an orange in my apple basket!
}
Consequently, you should consider T<A> and T<B> as completely unrelated types, regardless of the relation between A and B.
So how could you solve the issue you’re facing? In Java and C#, you could use respectively bounded wildcards and constraints:
//Java code
Bar(Container<? extends Interface) {...}
//C# code
Bar<T>(Container<T> container) where T : Interface {...}
The next C++ Standard (known as C++1x (formerly C++0x)) initially contained an even more powerful mechanism named Concepts, that would have let developers enforce syntaxic and/or semantic requirements on template parameters, but was unfortunately postponed to a later date. However, Boost has a Concept Check library that may interest you.
Nevertheless, concepts might be a little overkill for the problem you encounter, an using a simple static assert as proposed by @gf is probably the best solution.
* Update: Since .Net Framework 4, it is possible to mark generic parameters has being covariant or contravariant.