What is a radar fix?
Since this an FAA instrument approach procedure, this answer is specific to the FAA.

The RADAR label indicates that these fixes are marked on the approach controller's screen and he/she can advise the pilot when the aircraft is over the fix.

The use of Radar for arrivals and approaches is outlined in FAA JO 7110.65, Chapter 5, Sections 9 and 10. FAA Order 8260.19, paragraph 8-2-5(a) states that "Radar vectoring may be provided through any approach segment up to and including the final approach fix."

You'll note that the approach plate does NOT indicate RADAR REQUIRED because it is not the only method of determining or defining the fixes. In this particular approach, arrival at a fix can be determined THREE different ways: with Radar, LOC with DME (or GPS lieu of DME), and LOC with VOR radial. Per 8260.19, paragraph 8-6-6h, all IFR aircraft are assumed to have at least one VOR receiver, thus no equipment requirement note is required for this particular approach.

In practice, I've found that ATC will not call out crossing a fix unless you specifically request the service, though they will usually identify your position prior to hand-off (e.g. November 1234, two miles from SHAGY, contact tower on 120.5).