Why did you buy this property?
How long have you owned this property?
Did you do any research before buying it?
What are the adjoining row houses used as?
Do they have similar utility & basement height issues?
Who has been giving you this info?
What is it that you actually want to do? Rent this out as 2 units, 1 unit or perhaps sell.
How did you pick this architect & engineer? Have they modified similar row houses?
Do your tax bills show this as a single unit or as 2 units?
Does your building department show this as a single unit or as 2 units?
This are the type of questions that you need to get answered before deciding what to do with this property?
In order to make an informed decision on this building I would get pricing on the following;
1. dividing the utilities up
2. adding stairs from basement to 1st floor consider a spiral stair vs a straight stair
3. moving upper floor utilities up to 1st floor if this eliminates having to provide basement access
4. lowering existing basement floors to gain head room