Certainly if a transmission eigenstate has a large amplitude in the opposite of the system compared to from where it originated, it means it contributes a lot to the transmission. However, this is just for a particular k-point, energy, and transmission eigenchannel. The total transmission as function of energy is obtained by summing over k-points and channels, so you could in theory have, at one energy a single strong transmitting mode, and at another energy several smaller, but their sum might be larger than the single one. So there is no direct correlation, but of course they are related.
