I don't think there is anyway to control this but why do you need to restring it in illustrator?
What work flow is it that you do anything in illustrator that you couldn't do in microstation first. After all it just becomes a picture for printing once it has become a pdf?
If you wanting to measure things then put the lengths in the cad work.. or if other 3rd parties are using software other than cad to measure with then get them to use Bentley Redline instead. It is a powerful viewer tool for cad files that can measure ,draw attach ref files etc and free to select subscribers who can sponsor unlimited numbers of other free users ie engineers, contractors, subcontractors even clients to view your drawings with...