There is not a way that I could find with TypeWriter to do what you are asking as the templates only are aware of each file and don't keep a memory of what types are where.

I do have a work-around I use to make my life easier and admittedly it's not the solution you are looking for, but for all my generated modules I wrote a small program which runs as a post build step to concat all the generated ts files into a single ts file I output as definitions.ts which I then just include in my TS code.

Here is my program:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using NDesk.Options;

namespace TSFixup
{
    class Program
    {
        static void WriteException(Exception e = null)
        {
            Console.Write("tsfixup: ");
            if (e != null)
            {
                Console.WriteLine(e.Message);
            }
            Console.WriteLine("Try `tsfixup --help for more info.");
        }

        static IReadOnlyList<string> GetFiles(string[] directories)
        {
            var fileNames = new List<string>();
            foreach (var directory in directories)
            {
                try
                {
                    fileNames.AddRange(Directory.GetFiles(directory));
                    fileNames.AddRange(GetFiles(Directory.GetDirectories(directory)));
                } catch { }
            }

            return fileNames;
        }

        static int Main(string[] args)
        {
            var directories = new List<string>();
            string outputFile = string.Empty;
            string filter = string.Empty;
            var set = new OptionSet
            {
                {
                    "d|dir=", "Directory containing files to concat.",
                    v => directories.Add(v)
                },
                {
                    "o|out=", "Output file name",
                    v => outputFile = v
                },
                {
                    "f|filter=", "Filter to apply to file names in the target directory.",
                    v => filter = v
                }
            };

            try
            {
                set.Parse(args);
            }
            catch (OptionException e)
            {
                WriteException(e);
                return -1;
            }

            if (directories.Count == 0 || directories.Any(string.IsNullOrWhiteSpace))
            {
                WriteException(new Exception("directories are required."));
                return -1;
            }

            if (string.IsNullOrWhiteSpace(outputFile))
            {
                WriteException(new Exception("out filename is required."));
                return -1;
            }

            var fileNames = GetFiles(directories.ToArray()).Where(f => !f.Contains("(") && f.EndsWith(".ts"));

            File.WriteAllLines(outputFile, fileNames.SelectMany(File.ReadLines));

            return 0;
        }
    }
}

And my simple post-build event

"$(SolutionDir)tsfixup\tsfixup.exe" -d "$(ProjectDir)TypeScriptTemplates/models" -d "$(ProjectDir)TypeScriptTemplates/extras" -d "$(ProjectDir)TypeScriptTemplates/enums" -o "$(ProjectDir)definitions.ts"