My eBike came with an adjustable bar/stem. If I remember correctly the brand is Promax. Anyway, it moves up, down, forward and back. Can easily be changed on the fly, and has been flawless so far. It almost seems like a different bike going from relaxed to the more aggressive positions. Works great for me.
In the case of the Pedego (pics above), the OEM cables were extra long to accommodate the swept back cruiser style handlebars. The cable lengths were ideal for the stem riser and BMX bars. This may not be the case for other ebike styles however and longer cables may be necessary.