Research has shown that the type of substrate used during cardiovascular work makes little overall difference on fat loss. This is most likely due to the fact if one relies mostly upon fat stores during cardio (i.e. low intensity cardio), the body will burn predominantly glucose at other times of the day. Likewise, if one mainly utilizes glucose for energy during cardio (i.e. high intensity cardio) the body will customarily rely on fat at other times of the day in order to spare muscle glycogen.
Training in and of itself causes the body to preferentially spare muscle glycogen and burn fat. It makes sense that one should strive to do their cardio on their 'off days' from lifting (as to not further hinder their recovery), and plan their carbohydrate intake similar to their lifting regime.
Cardiovascular work will increase nutrient partitioning towards muscle tissue and away from fat tissue. One should take advantage of this by consuming the bulk of their carbohydrate intake around this time. The benefits are that these nutrients induce fat storage, but will rather be stored in muscle tissue.
Why would you want to deny your muscles nutrients at the most crucial time of the day, but then provide them during rest? It does not make sense. Treat your cardiovascular work like your lifting.