Yes. A voltage divider like the one you showed will work. One thing I forgot to consider is the voltage drop across the regulator. Since your source is of 30v and you want 15 -0 -15, you cannot (and no need to) use any voltage regulator. A simple setup with just 2 resistors like you showed can do the job. But the problem is that if you reduce the resistor values, a lot of current will drain. You need less than 5 ohm resistors and that will drain a huge current between 30v to 0v.
A voltage divider is good for low current supplies. For such a high current, I think you need a 1:1 transformer, where you can set the 'center tap' as common. This one you can build by your own, if you have that resource.