If the floor plan is to scale, then I see no problem in term of size.

Yes, I would say the main factor affecting the cost for this case is the location of the manhole.
This guest bath is not connected to any vertical stack. The plumbing work involve here would be direct discharge to sewerage main via under ground and tapping of water from laundry.

He want to relocate to Utility 1 not 2.

Not likely to be 40k. Other than the M&E works, builder works should be
1) Hack existing concrete floor/wall and finishes
2) Excavate a trench to lay the sewerage pipe.
3) Back fill of the trench
4) Cast back the floor and build back the wall (If any) together with the finishes.
5) Hack chasers at wall to lay the water pipe. (Can skip this if you opt for expose pipe)

These should more or less about it.

Should be as what weikee estimated 15-20k.

But you know la, OPAR price can be very unpredictable.