Praise be to Allah, the Lord of the Worlds.
The right to a turn is amongst the customary rights. Scholars call it "Right of priority. A specialization to which a person becomes entitled by being the first to own it, and it is impermissible to sell. However, the right to a turn isn`t owned by the person entitled to it, in addition to the fact that it is neither a material nor a benefit, thus it can`t be sold. Rather, it is a mere right. Therefore, he either uses it or gives to someone else free.
About the priority to a specialization and not ownership, Al-Shirbini says, "Our correct opinion is that it is invalid to sell that right, as stated al-Juwaini and other scholars. In addition, it is invalid to gift it, as stated al-Mawardi contradicting al-Darmi. This is because the right of ownership can neither be sold nor gifted unlike the right of preemption."{Moghni al-Mohtaj, 3/504}.
Al-Shafie{May Allah have mercy on him} says, "If he gave money to one of his wives so that she gives up her right in his staying with her that night and she accepted, then she should give it back and it is impermissible that she takes it. Also, he should have stayed at her place as this is portion between wives. This is since her turn, for which he gave her that money, is neither a material nor a benefit."{Al-Umm, 5/203}.
In conclusion, it isn`t permissible for an employee to give up the right to his turn in collecting that Jamiah against receiving a compensation; particularly since the idea behind creating such Jamiahs is similar to a loan`s. And Allah the Almighty knows the best.
Note by translator: The most common term for this sort of thing-Jamiah-is savings pool or money pool.