John,
Lots of narrow gauge steam in Germany on a daily basis, no need to wait for a plandampf! Of course, if you go for a plandampf be sure and stay for some narrow gauge. The meter gauge HSB in the Harz is fantastic, but the 75cm lines down around Dresden are pretty cool too! I've never been to the two lines up on the North Sea, but one is 900 mm (about 3 foot) and features some interesting street running.
Dave Goodheart (who passed away recently) distributed a wonderful tape called "Steam to the Borders" that was shot by a British film crew just a few months before the wall came down. This tape covers all of the East German narrow gauge lines still operating at that time (Amazingly, almost all are still operating today!). I believe some friends are still carrying on Dave's business to clear out the remaining inventory, so you might still be able to get a copy.
Michael Allen