well, it can be LOS or it can be NON LOS… if there is LOS, then the first signal to arrive is LOS (the direct path is always the fastest). If there is some NLOS arriving almost at the same time (within the same wavelength), then the signal will be a mixture.
if there is NLOS, then the LOS cannot reach the BTS. So the first NLOS to arrive will be used to compute the TA. And the first LOS to arrive might be a mixture between different NLOS.
But why do you ask this question ? Maybe there is another question behind, isn’t it ?