The German Interior Ministry came out this afternoon (17:30 local) and announced that they were putting temporary border controls back into place. Based on the way that the way that the statement was made.....they intent to bulk up the region in the south.....between Bavaria and Austria. There's also the hint that trains will be stopped and passengers will be asked for passports.
The Passauer Neue Presse (a Bavarian newspaper) said that the federal authorities will checking the trains going from Bavaria into Austria.
News reports say that Bavaria has requested 21 squadrons of the federal cops. I spent a half hour looking up the typical manpower of a German police squadron, but there's not much information on how it relates to number. A number US Air Force SP squadron would be roughly 120-personnel, so I would assume the same for the German cops. As for approval for the Bavarian request? Nothing, and it might take a week for the Berlin folks figure up the cost and how they would send these folks down to Bavaria (hotel cost alone would be in the 7-figure range a month easily.
This border change episode? It's being applied as a temporary measure. No one says it'll be permanent.
The potential success rate? Zero.
If you were a refugee and walking across the border.....you'd survey the Goggle map on your cellphone and pick a walking path without much access to civilization or urban areas. There are literally hundreds of such paths in Bavaria....giving you access to Austria. You pick such a path, and the odds are....whatever border guards are around.....will be near the autobahn or major roads. It'll take less than two weeks for the public to realize that this border control announcement was just a public relations thing, and has very little impact on stopping people.
How many personnel would it take to run an effective border situation? I'd take an educated guess that it would get into the 10,000 range on top of the present border force....very easily, and the German federal government would not be so willing to put this much time, effort and funding into such a matter.