BR allows upgrades on award tickets. With the miles needed to upgrade, though, you would be better off initially booking the premium ticket (unless you want only a one-way upgrade).

It's actually comparable to UA's system as far as the raw ratios are concerned, e.g. US-Asia XY=60k miles RT, XC=90k miles RT, Y->NC upgrade = 30k miles EACH way. The difference is that on BR, you actually have the option to do the unfavorable-rate upgrade at 60+30+30. Maybe it comes in handy if someone gives you an XY ticket as a gift but you don't do economy travel.