Since I couldn't find a solution I handled it manually by following code:

In my posted method in the controller I added following code for setting the value for the checkbuttons and radiobuttons as a custom value in my XFormData object:

// Check if the answer is correct, all correct option got the value 1
            foreach (XFormsFragment fragment in xFormpostedData.XFormFragments)
            {
                // Radiobutton list
                if (fragment.GetType() == typeof(EPiServer.XForms.Parsing.Select1AsRadiobuttonFragment))
                {
                    EPiServer.XForms.Parsing.Select1AsRadiobuttonFragment fragmentObject = (EPiServer.XForms.Parsing.Select1AsRadiobuttonFragment)fragment;
                    IList options = fragmentObject.Options;

                    foreach (SelectOption option in options)
                    {
                        if (option.SelectedItem)
                        {
                            formData.SetValue("RadioButtonValue", option.Value);                                                    
                        }
                    }
                }
                // Checkbox list
                else if (fragment.GetType() == typeof(EPiServer.XForms.Parsing.SelectFragment))
                {
                    EPiServer.XForms.Parsing.SelectFragment checkBoxList = (EPiServer.XForms.Parsing.SelectFragment)fragment;
                    IList checkboxOptions = checkBoxList.Options;
                    var test = ConcatenateCheckBoxListValues(checkboxOptions);
                    formData.SetValue("CheckBoxList", ConcatenateCheckBoxListValues(checkboxOptions));                     
                }
            }

private string ConcatenateCheckBoxListValues(IList options)
        {
            StringBuilder sb = new StringBuilder();
            char[] characters = new char[] { ' ', ',' };
            String trimmedString;

            foreach (SelectOption option in options)
            {
                if (option.SelectedItem)
                {
                    sb.Append(option.Value + ", ");
                }
            }

            trimmedString = sb.ToString().TrimEnd(characters);
            return trimmedString;
        }

And in the Index method when loading a form with posted data:

// Load existing formdata if exists for current user
            XFormData currentUserXFormData = GetPostedDataForCurrentUser(currentPage.Form);

public XFormData GetPostedDataForCurrentUser(XForm form)
        {
            IList formData = form.GetPostedData();

            foreach (XFormData data in formData)
            {      

                // Will max be on hit
                if (data.UserName == HttpContext.User.Identity.Name)
                {
                    return data;                   
                }
            }

            return new XFormData();            
        }

And then I return desired value to my model in the Index method:

currentPage.XFormSavedValues = valuesToCheck;  // The values that is !string.isnullorempty from custom data from currentUserXFormData 

And then I checked checkboxes and radiobuttons with Jquery in my view as follows:

$(document).ready(function () {      

        var valueToCheck = "@Model.CurrentPage.XFormSavedValues";

        //Function to check the checkboxes with the saved values
        var valuesArray = valueToCheck.split(',');
        var index = 1;
        $('input[type=checkbox]').each(function () {
            if ($.inArray("" + index + "", valuesArray) >= 0) {
                $(this).attr('checked', 'checked');
            }
            index++;
        });

        //Function to check the radiobutton with the saved value
        if (valueToCheck.indexOf(',') == -1) {
            $(":radio[value=" + valueToCheck + "]").attr('checked', 'checked');
        }
        
    });

/ Johannes