The ReflectionUtility appears in the HyperShade in the `Create mental ray Nodes/Miscellaneous` tab. If you don't have this tab than you have to create an environmental variable. The easiest way to do it is probably to open the maya.env file (in the user’s profile/maya directory), and add the following line to the end:
MAYA_MRFM_SHOW_CUSTOM_SHADERS = 1
Restart Maya and it will enable the display of MR nodes.
The easiest way of using the shader is by connecting it to any other material's Reflected Color channel. Set the material's Reflection Limit value under Raytrace Options to 0, to disable the reflection computation of the base material. (Otherwise the two reflections would appear overlapping each other.)
You can connect it to a surfaceShader’s outColor, and this way the shader works as a useBackgound material, and only displays the reflections. If there is anything connected to the material’s or the camera’s MR Environment Shader channel, than the environment is sampled if the ray does not hit an object or when the raytrace limit is reached.