Are you asking if a field boundary created from a lower end GPS system can be used successfully with an RTK based application unit?     In my experience, yes... this is really not a problem.  You find find that the boundary is off by as much as a couple of meters from an RTK boundary at some locations, but you are operating a machine that is usually at least 30 feet wide, and for many applications, much wider than that.  

The biggest issue you will have is crossing waterways with auto-boom stuff.  If you don't drive around the waterways first, it is possible that the waterway boundary from your ute might be off by a couple of meters, and this would cause the auto-boom to kick on while you are still in the waterway, or kick off before you get to it.   I think when you drive around the waterways, you are able to apply an extra "buffer" to the waterway side of your swath that would prevent a nozzle from kicking on when it extends past the area already sprayed (like swinging a boom over the edge of a field on the turn).

Other people on this forum are MUCH more qualified to address this than am I, though.