Among other things, the text tells us that sheep (people) who hear (believe and respond to) the shepherd (Christ) do so because they are his, whereas people who do not believe in Christ do not because they are not his. What must be determined in order to understand the figure properly is if is it saying that the mere fact of ownership (which could be seen as akin to election) causes response in sheep. In other words, does ownership (election) of the sheep cause them to hear the shepherd or does "hearing" merely establish that they are, in fact, owned by the shepherd (something akin to a brand).
One viewpoint sees a cause, where the other sees a description.
Sheep in the real world imprint to their shepherds during the process of being raised and tended by those shepherds. Apart from the ability to imprint at all, there's nothing intrinsic (or genetic) in a sheep that connects it to its particular shepherd. Only the relationship that has been established over time between them connects one to the other. The preference resulting from discerning hearing in sheep is developmental, so the hearing of the sheep presupposes a trusting relationship with the shepherd.
Now, the Pharisees and others in the audience were oblivious to whatever points Christ was making by using this figure. They missed the gist of the allegory all together: namely, that Jesus (and not any other including them) is the means for those that follow him to have life and all it brings. They had shown no inclination to accept him as a shepherd (they called him a raving lunatic), nor any willingness to develop a relationship with with him that would have tuned them to his voice. Even his miracles did nothing to elicit any kind of trust from them.
All those God, the Father, has given to Christ as his sheep (followers) will trust in him, whereas those who have no faith in Christ cannot possibly be a follower of Christ. If one has faith in Christ it means that one is one of the ones the Father gave the Son, if not, that one isn't--mere description. I don't think Christ would have appropriated this figure to demonstrate something the figure would not have demonstrated to any shepherd in his day, nor something that would fly in the face of later scripture. It is not saying that mere ownership (or election) causes trust, but merely that trust in Christ demonstrates that one is part of the fold his Father gave him.
This is accentuated from the viewpoint of the shepherd in vs. 11-13. Though sheep will not listen thieves and robbers, they will listen to and follow a hireling who, as their shepherd, has formed a relationship with them. However, only an owner, who is actually a shepherd too, will rise to the level of a Good Shepherd by hazarding all dangers in order to save them. So relationship, not ownership, grows faith, although ownership is what makes faith truly beneficial.