Ran into this issue, struggled with it for some time and was about to post a question when I stumbled on the obvious solution. May help someone in the future
I enabled scaling by pressing the R key. Now with blender shortcuts, I can press and hold S and simple move the mouse for uniform scaling. This does not work with Maya shortcuts. With the scale manipulator active with Maya shortcuts, how do I scale uniformly?
Solution: When the tool is active, there are three axis with cubes all emerging from a grey circle. The grey circle is similar to the center cube in Maya scale tool. Drag from the circle to get uniform scaling.