Custom Columns are not restored, even if the SharePoint List restores successfully.
Recently I came across a case where the one of our customer was facing an issue on restore of SharePoint List that contained custom columns.
I tried reproducing it in house but I could not, then I asked for output of spprobe2010.exe, from the output I could see that the customer has upgraded SharePoint to cumulative pack - 14.0.6134.5000.
I upgraded my SharePoint setup to same cumulative pack and tested again and voila!!! The issue is reproduced at my setup. I investigated further and found that there are some underlying SQL changes in the cumulative pack.
The fix to this has been provided in an ET 3202205.