It is highly recommended for every Shia Muslim to pray with Muslims from other sects in their congregational prayers, but we need to recite Sura Al-Hamd and other Sura for ourself. Such Salaah will be valid if it was performed inside the time not before it.
Jum'a prayers with non Shia Muslims is good but we need to recite Dhuhr Prayer as well.
Wassalam.