It looks like the upgraded transformations should use the GetSharePointFileUrl method in the TransformationHelper class. To replace the SplitSharePointField function, the transformation can simply use a String.Split. Here's an example from an out-of-the-box transformation.
<%-- The Author is a lookup field containing ID and value separated by semicolon --%>
Author: <%# Eval("Author").ToString().Split(new[]{';'})[1] %><br />