You certainly used to be able to, as we did last year. But more recently people have reported being unable to use these, seemingly because of the unlimited alcohol available. When you use a HB voucher at Auberge now you are restricted to one glass of wine, whereas when you pay cash you can have more. At The Steakhouse they are unable to restrict the wine like this as its on a help yourself basis so it could be why they stopped it.
Having said that these things do vary from CM to CM so if you haven't made your reservations you could check when you are there.