Well, as this is under an actively used Catholic cathedral, and Catholics typically like to do our services on top of our saints, I imagine the clergy and the diocese has something to say as to how the bodies are treated.
Interestingly, always: a Catholic church contains an altar, the literal definition of which requires that it either contain or support the relics of saints. In other words, there are either bones in the altar or something which touched the body of a saint. Neat how the tradition had continued for so long. I wonder about how they manage to reliably source the material as well as to ensure its provenance. Supply chain is an issue everywhere!
Yes, indeed, there's always some portion of a saint (or something having touched a saint) in the altar, stemming from the early days of the Roman church when, during Roman persecutions, the church would hold Mass/Divine Liturgy over the bodies of martyrs in the catacombs.
However, most churches don't have full bodies anymore, for obvious reasons. However, when the altar is stripped (for example on Good Friday). If you were invited into the sanctuary... you would be able to see a stone, on which there is inscribed several crosses. Under each cross is a relic, set into the stone. The priest consecrates bread / wine over the stone.
In terms of provenance... you can't sell a relic, but most monasteries, shrines, the Vatican, or other places that have burial records, will provide relics upon request, if available. Orders keep careful details of their martyrs and saints. So for example, a Dominican parish will often ask a Dominican priory with burials of a Dominican saint for a relic. We have indeed even entered the modern age where some monasteries / priories / convents even let priests request relics online!
