Would a carbamate be attacked twice by an alkyl lithium cuprate reagent? For example, say you react ethyl carbamate with methyl-$\ce{LiCu}$; would two methyl groups displace both the amide and the ester, creating an isopropyl alcohol?
I don't think so, carbonyls don't typically react with Gilman's reagent (dimethyllithium cuprate) unless the carbonyl happens to be $\ce{{\alpha}-{\beta} }$ unsaturated. So I would expect no reaction under normal reaction conditions.