I'm assuming that these songs appeared in the movie version, it's been awhile since I've seen it.    You have a couple of issues here.   You will need to get authorization from Tams to be able to include the songs in your production AND from the rightsholders of the two songs in question.

If I were you I would simulataniously seek permission from both.  For the songs themselves you may need to go to several resources but a couple of places to start would be SESAC at www.sesac.com  and ASCAP at www.ascap.com.

Now the next thing you have to ask yourself:  is this all worth it for two songs?   Will these songs really enhance the show or improve your audience numbers?    Do they do anything to move the plot, tell the story or offer any kind of character enhancement that can't be achieved from what's already included in the script other than it being nice that they be included?  

It also appears from the Tams web site that two versions might be available, the original 1966 and the revised 1987.   Do the songs appear in one version and not the other?  If so then you may want to do the one in which they appear.

Good luck!

Please, no rants ; but you ask some good questions.  I went to both websites you mentioned and couldn't find a thing.  ASCAP was a bit easier to search than the SESAC . . . but either way, it doesn't look like we can get permission from anywhere other than TW?. 

Also, I find it highly frustrating that these songs aren't available when other songs from the movie ARE in this 1986 revival.  what makes these 2 songs so different from the other ones from the movie??  The questions you ask of Ziwiki about the songs:  Mein Herr is practically a show stopper of a number, dance-wise, you're not going to find a better one to choreograph in the show.  And it is one of the songs that lays the land for the bawdiness of the cabaret.  As to 'maybe this time' . . this is a great piece, too.  Sally Bowles sings it and it's a great push for her character development..gives you a really nice and poignant look into her inner person. It's a time we get to see the 'real' sally. It'd be sad to see that go, because all of the other songs she sings are upbeat/racy/comic other than the title song. 

And then i'm also really annoyed that there are those of us out there who are trying to do the right thing with this extra material, and are willing to pay for it, and then to see that there is proof out there that others are doing it and potentially not getting roasted for it.  It's maddening, because I feel like we are doing the right thing, but we get to 'suffer' (for lack of a better word) by not getting to do this great material.  But, I appreciate your responses on where to go to look for further info.  Thanks,