Thanks for the link. It seems to me there are two sets of questions:
1. What happens when you import data written by Arc directly into 9? Does it import correctly with everything lined up?
2. Multi-step interoperability issues. What happens when you do a multi-step chain: Arc->8, 8->9, 9->8, 9->Arc, etc.?
It seems to me that we first must answer 1. above, for these reasons:
a) 9 users who want to import files written by Arc do so directly. They do not first import into 8 and then import from 8 into 9.
b) If 9 imports the Arc-written data correctly, the primary task is done.
c) If 9 does not import the Arc-written data correctly, that can be fixed in a day.
d) If the interest is not getting Arc data into 9 but instead is testing interoperability between 8 and 9, knowing what happens Arc -> 9 and Arc -> 8 helps narrow down problems when doing 8 -> 9.
If we assume the initial export from Arc was correct (a risky assumption, but let's start with that), the first thing to verify is if pairwise interchange Arc -> 8 and Arc -> 9 are both correct.
I've asked before and for some reason have not gotten an answer: What do you mean by "Everything is fine in M9, all is aligned" ?
When importing the sample data set from the link, there are no dots in the c914_mnt raster against which alignment of the points in the buf drawing can be checked. I see no obvious way to tell if in the direct import into 9 that c914_mnt and buf are correctly aligned or not.
Overlaying c914_mnt with partial transparency over a google terrain layer seems to indicate it is in the correct place, but not to a level of detail where you can say plus or minus 1 meter it is exactly correct.
So, let's rephrase that key question: when you import the shapefile and the tif directly into 9, are they imported correctly, does everything line up as expected, and, how can you tell whether everything is correctly aligned or not?