Move Topography lines down to 0 grade level?

We receive drawings from a Survey Company, all the drawings come to us in
Acad 2000 format. The problem we have is that we need to move all the lines
back down to "0" Z Axis to edit them. I thought I saw this addressed before,
but I can't find it anywhere in the news group. I tried using a program
called:
FIXLINES.LSP -- Moves endpoints of all LINE objects to 0 elevation.
(c) 1998 Tee Square Graphics

But it does seem to change the dwg (not the lines I need to move at least)
I think the Surveyor uses the Autodesk Land Developer Product (LDT I think?)
..

Is there a routine that can accomplish this. Or can the Surveyor "Flatten"
the dwg prior to sending it to us?

(BTW I did try to use Flatten command and got no results) TIA

 

--comments inline--

Are the entities really lines? When you list one, what does it say?

think?)

If you're trying to change his contours and can't, chances are they're
AECC-Contour entities; not sure why you'd want to change the surveyor's
work, but you can either:

1) Ask the surveyor to convert the contours to lwpolylines for you.
2) Obtain the object enabler for land desktop from the autodesk website.

 

You must Explode an 'ACAD_PROXY_ENTITY' before you can edit it. We get
these here all the time. I first explode them, then use PLJOIN (express
tools) to turn them back into polylines. You can then use FLATTEN (express
tool again) to give all the contours a '0' Z elevation.

Hope that helps...