Yes it is feasible.
I am mixing several frame buffer with mayatomr (no stand alone version)
The problem is that as far s I know, you can't directly say in your .mi file that you are using several frame buffer (maybe with an output shader as max says on one of the Maya thread, to be tested for Maya)...
Maya doesn't know how to parse this information.
So you have to do it manually by using the miDefaultOptions node.
Do inMEL :
then in the attribute editor, you can add a frame buffer and choose its settings (RGb,RGBA,Z etc...)
Then the shader code to store/access a frame buffer is :
//In a shader (material, texture..)
//Put something in user frame buffer 0
miColor ToonColor; //initialized somewhere else
miBoolean bResFB0 = mi_fb_put(state,0,&ToonColor);
if (! bResFB0)return miFALSE;
//Then in an output shader
miImg_image *fb_color = mi_output_image_open(state, miRC_IMAGE_RGBA);
miImg_image *fb_colorToon = mi_output_image_open(state, miRC_IMAGE_USER+0); /User frame buffer 0
miScalar ToonCoordXG, ToonCoordYB; // initialized somewhere
mi_img_get_color(fb_colorToon, &ToonG, ToonCoordXG, ToonCoordYB);