Question about traps for ejector system

I recently purchased a home and am finishing the basement. A bathroom was roughed in, with an ejector system. My question is about the connections for the tub. The overflow pipe comes up through the slab, and connects to a T junction below the slab. One side of the T goes to the ejector pump, the other side is open, for connecting the tub drain. My concern is that there is no trap on the overflow, and the plumbing inspector has confirmed that every fixture needs to be trapped (though he hasn't looked at my setup in person). Can anyone tell me why the system is connected this way, and how I might fit a trap in here? Thanks!

The trap for the tub should connect to the upper end of the burried (combo) fitting. The riser coming out of the floor is the vent which should be run thru the roof.

You bring up a good point about how the system is vented. After some poking around down there, I determined that there are two separate vent pipes coming up out of the slab back by some other utilities. You can see them in these pictures. The larger one vents the sink and toilet drains while the smaller one vents the tub drain I am having problems with. I included a picture looking towards the bathroom showing the locations of the tub and sink drains. I bet you can guess where the toilet drain is

From the way that set up looks in the ground,,,, I believe they intended for the line that is stubed up to be your tub vent. The open end of that tee should proceed to the tub waste. YES it should be trapped directly under the tub .

Going to be a nice size bathroom !

If it were me I would put a st 90 on the end of the that T and aim it towards the tub then put a glue trap on the 90. If there will be access to the trap area when the project is complete you could use a male desanco and then attatch a lite weight compression trap to the desanco.
If you have the room and everything is aligned right you might be able to glue the trap directly to the T and swing the trap to the tub waste but I can't tell from the pic where the tub is going to end up.
Cass