Can SetExternalTexture be used with a Texture2D in stead of TextureRenderTarget2D?

I don't need a movie to display like in the rearviewmirror demo, just single Textures that I get from screenshots.

I'm handing one in and it is returning true as a result, but the texture doesn't change.

I do a test where I draw the Texture2D to the HUD also, so I know the Texture2D is valid.

[Edit] The answer is yes.

But... It only works for me with a packaged Texture2D, such as Texture2D'UI_FrontEnd_Art.GameTypes.___TeamDeathma tch', it doesn't seem to work with a dynamically created Texture2D even though the Hud's Canvas can draw the same created Texture2D.