I've used the method described at Adding a filter to the BizForm data listing page, and it also works will with version 5.5R2.

Unfortunately in version 5.5R2 the filter parameter isn't passed through to the export dataset (/CMSModules/BizForms/Tools/BizForm_Edit_Export.aspx.cs - line 71 - dsFormData = genConn.ExecuteQuery(className + ".selectall", null, null, null);).

Is there a way I filter the export dataset in version 5.5R2?