Maya Curves

Maya curves can be tagged to be rendered.  Create curves with one of the curve tools under:

Create > Curve Tools

In the Attribute Editor be sure and assign a material to your curves:

That's it!  You should see the curve in your render.

Paint Effects

This image is rendered entirely with curves generated with Paint Effects.

To create Paint Effects, open Maya's Visor window: Windows > General Editors > Content Browser.  Find the Paint Effects tab, click on a brush type in one of the folders, and then draw in the Maya viewport.

Paint Effects strokes that use a Brush Type "Paint" are rendered directly as curves by RenderMan.  It isn't necessary to translate to a mesh, although in some cases you may wish to do that.  You can find the brush type on the brush node after drawing a stroke.

After creating a Paint Effects stroke a couple extra steps are required to set up a RenderMan material for rendering.  Shading for Paint Effects brushes is not fully translated.  However, a Cs (color) primitive variable is emitted for the curves, so you can make use of that in a material assigned to the stroke. PxrPrimvar > Color Input

In the PxrPrimvar make the type a color and use Cs. This will pass the Paint Effects color to the material. You can then hook this up to a material assigned to the stroke in the RenderMan rollout in the Attribute Editor.