Dual switching power supply with centre tap transformer
You can easily get hold of linear regulators that truly regulate a negative supply voltage and hence can easily be wired together with a positive regulator just like in your picture (which I attach here for ease of explanation): -




  I was wondering whether something like this is possible using two
  switching regulators


Here's where the problem begins - almost all (if not all (contradiction later)) buck switching regulators are based around regulating a positive voltage with respect to 0 volts. The upshot of this is that if you had a transformer output with two seperate secondary windings it makes things doable. In short, (unless someone else knows of one) there is not buck switching regulator equivalent of an LM337 (or a 79xx type) regulator.

It's probably better to use the full output from the secondary (ignoring the centre tap) and have both a positive regulator and an inverting regulator; the inverting regulator is still fed a positive voltage and 0 volts but, in this special case, it produces a negative voltage. Here's an example: -



Having said that I'd never found a truly negative switching regualtor, in searching for a fairly powerful inverting regulator, I found this and it's certainly worth considering because it's from a reputable source: -