What is the intended plan with this basement rough-in plumbing?

I think Jack is right--here looks to only be one water line so that maroon would be for the toilet. I would expect the vent to be in the wall, and the 1-1/2" or 2” pvc to be a sink drain. The toilet was probably planned to be at a 45 degree angle.

A sink requires a outlet within 36” so that electrical may be for that once the studs have been installed on the stem wall. With only one water line an on-demand or small water heater may have been the plan.

The OP shows a typical corner in a bathroom with the toilet waste located near the corner.

Based on that, the code requirement (See ICC Figure 307.1) for clearances is 15” minimum from center of toilet to side wall or obstruction (cabinet, tub, etc.) Here is the code layout:

https://shop.iccsafe.org/media/wysiwyg/material/8950P235-sample.pdf

Please notice that the 15” side clearance runs all the way to the wall. This is impossible with a corner toilet. See American Standard CORNER toilet:

https://assets.supply.com/ul_pdfs/415662_installguide.pdf

As you can see, the tank is about 20” wide where it meets the wall. In order to meet code, the tank would need to be 30” wide.

So, let’s assume Ed and the OP intends to build a diagonal wall and install a standard toilet on that wall. In order to meet code, the wall would need to be a minimum of 30” (actually it would need to be 32” after gypsum board is installed and still obtain the 30” minimum clearance.)

In order to build such a wall, it will need to be a minimum of 16” out from the corner...and clearly it would cover the existing rough-in.

Summary:

1) A corner toilet does not meet code, and

2) The OP cannot build a diagonal wall and meet the code with the required clearances, unless they chip out the concrete slab and move the existing rough-in.

(Btw, in my comments, I didn’t say a corner toilet can’t be installed or is never installed, I said it doesn’t meet code. I’m surprised Lane County allowed such an installation, because the are known for strictly following the code.)

Here's why I think a corner mount toilet meets code. This is takn from one of the references Lee Sam provided. The measurements in RED were scaled from the American Standard drawing and may be off by an inch or two.