Q: Including Custom Columns when retrieving Content Type Using the Lists web service I am retrieving a content type as follows;
var contentTypeWithFields = listsService
    .GetListContentType(listId, contentType.ID);

However, the result does not include any information about custom columns which have been added to the list (and which are applied to all content types).
Is there some way that I can retrieve information about these custom columns?

A: you can do it in more ways.
For example by powershell you can write something like this:
PS > $web = Get-SPWeb "http://nevecrino:26295/"
PS > $web.Fields["MyCustomField"]
FieldValueType              : System.String
PreviewValueTyped           : CodiceFiorital field value.
FieldRenderingControl       : Microsoft.SharePoint.WebControls.TextField
DifferencingLimit           : 1500
FieldRenderingMobileControl : Microsoft.SharePoint.MobileControls.SPMobileTextField

.....
and more and more information
