Suggestions wanted with Lists or Enumerators of T when inheriting from generic classes

public interface IOtherObjects;

public abstract class MyObjects<T> where T : IOtherObjects
{
   ...

   public List<T> ToList()
   {
       ...
   }
}

public class MyObjectsA : MyObjects<OtherObjectA> //(where OtherObjectA implements IOtherObjects)
{


}

public class MyObjectsB : MyObjects<OtherObjectB> //(where OtherObjectB implements IOtherObjects)
{


}

class B : A
class C : A

List<B> listB;
List<C> listC;

List<A> listA = listB.Cast<A>().Concat(listC.Cast<A>()).ToList()

foreach(var myObject in myObjectsList)
    foreach(var obj in myObject.ToList())
        //do something

// Original Code Snipped for Brevity - See Edit History if Req'd

public List<OfType> TypedList<OfType>() where OfType : IOtherObjects
    {
        List<OfType> rtn = new List<OfType>();

        foreach (IOtherObjects o in _objects)
        {
            Type objType = o.GetType();
            Type reqType = typeof(OfType);

            if (objType == reqType)
                rtn.Add((OfType)o);
        }

        return rtn;
    }

public abstract class MyObjects<T> where T : IOtherObjects
{
    List<T> _objects = new List<T>();

    public List<T> ToList()
    {
        return _objects;
    }

    public List<IOtherObjects> ToBaseList()
    {
        List<IOtherObjects> rtn = new List<IOtherObjects>();
        foreach (IOtherObjects o in _objects)
        {
            rtn.Add(o);
        }
        return rtn;
    }
}

public abstract class MyObjects<T> where T : IOtherObjects
{
    List<T> _objects = new List<T>();

    public List<IOtherObjects> Objects
    { get { return _objects; } }
}
#warning This won't compile, its for demo's sake.

List<A>.Cast<B>().ToList<B>()

interface IMyObjects : IEnumerable<IOtherObjects> {}
abstract class MyObjects<T> : IMyObjects where T : IOtherObjects {}

IEnumerable<IMyObjects> objs = ...;
foreach (IMyObjects mo in objs) {
    foreach (IOtherObjects oo in mo) {
        Console.WriteLine(oo);
    }
}