You will not have any problems if you are using a good quality switching power supply from someone like Phoenix Contact. We use switching power supplies for 4-20ma signals all the time. Just check the output ripple rating of your power supply, and if it is low you should not have any problems.
I do it all the time, never had any problems. Switcher power supplies output very clean power. Its the line side of a switcher that may have problems. I recommend using one with fileters too keep harmonics off the line side, such as Phoenix F series.
I use switcher supplies for most of my applications (for loop analog signals and digital signals). I've never run into any noise conditions, if that's what you're concerned about. The switcher suppy is typically smaller and dissipates a lot less heat than a linear supply. Just be careful of the output ripple specifications (usually greater 150mVp-p is bad for a +24V supply).
