You will not get a pastave since you cannot mix male DNA. For example (and for sake of argument), you have a White woman (human). She sleeps with a black man and an Asian man (I'm not trying to be racist....this is just for sake of argument). She gets pregnant. The baby will be either a Black-white mix or an Asian-White mix. The baby can only be fathered by one man. You will never find (in this scenario for example) a Black Asian baby from a White woman.
The same goes with your snakes. The babies from your normal female will be either mojave, pastel het pied, or normals (some het pied, some not het pied). If you get mojave babies, you know for sure that the mojave male sired them and they will NOT be het pied since the pastel pied and the mojave DNA do not mix (think of the Black-Asian example above). If your babies are pastel, they can only be sired by the pastel pied and WILL be het pied since the father was piebald. Now...you will end up with some normals as well. You cannot outwardly tell which male sired it. You could look for het pied markers, but those are not always reliable. Unlike the other person, I would not sell them as 50% het pied. They either are het...or they aren't. But since you don't know for sure, you will need to do the honest thing and sell them as plane jane normals. However, you could say they were possibly sired by the pastel pied and be het pied (or you could just say the father is either a pastel pied or a mojave and not say anything about what they might be het for). Then, the buyer can make the choice to buy a normal and try and prove her out if they wanted to. That saves you later if they don't prove out het pied and the owner comes back pissed off because you sold them a het animal when it really wasn't het.
I hope that made a little bit of sense...