Bad news:
It is not possible to view PLT files in AutoCAD. However, if the PLT file is in HP-GL format, you can use the PLT2DWG AutoCAD Express Tool to convert it.
That's what Autodesk says, got $149 US to buy Express Tools?
with no guarantee that it will work?
This probably won't work, but take an empty drawing, save it as DXF, rename the DXF, open it with a text editor and drag and drop your .PLT file into it. Erase any text that looks like plotfile identification and save it. Now open the .DXF file.
Try it, what have you got to lose? The drawing?