Use of external collaboration in masters I have recently finished a 4yr Bachelor in Physics and have been looking for a masters thesis(the masters program at my university is rather dumb - you just do research and the thesis).

A recently appointed professor has suggested a thesis to me to which I am partial - though it does not strike me as "THE thing I always wanted to do".

The thesis would entail a collaboration with an external research institution (Max-Planck Society for those familiar with the field).

I do not - at least for now - plan on following the project to a PhD (though there is that possibility) mainly because I think it is not quite what I am interested in.

My question is thus: Are such a collaborations be beneficial to a search for a PhD position in the future?

My plan is to get (the hell) away from my current university at the latest after the master thesis.
Yes! Such collaborations will generally help you apply for doctoral programs. 

Here are a few reasons why it will help you get into a grad program:


You will get more research experience which grad programs look for. 
You will have more opportunities to network with important people. 

These people will be able to write letters of recommendation for your grad school applications. 
You never know when these kinds of connections will help you....

You will have a better idea of what kinds of research or work you want to do, so you'll have a better idea of which programs fit you better. (Don't underestimate this.) 
You'll build your curriculum vitae (CV), which looks good.


Other Comments


If it's not a research position doing something related to what you want to be doing, that's okay: it's temporary. 
Don't take advantage of too many unrelated opportunities. If you bounce from project to project, without a unifying theme or good reason, it can make you look like you have commitment issues, and admissions committees may worry that you won't stay to finish your PhD with them. (This isn't meant so much for you, since you're just finishing, but for others who may be in a slightly different position.) 
Having a research experience at a national lab is a great way to find out how you like research in a non-university setting. In my experience, national lab work can feel like something between an industry job and a grad student job.