RegisterTemplateOverrides doesn't work with Calendar list

Hi

We have developped our own javascript to replace the Lookup fields in our App we published on Office Online.
It works fine with all lists, except Calendar Lists !
here is the code I have (the method SPFieldLookup_Edit is called correctly with all others lists) :

function _registerLookupFieldTemplate() {
            ULSpCg:
            ;
            var lookupFieldContext = {};

            lookupFieldContext.Templates = {};
            lookupFieldContext.Templates.Fields = {
                'Lookup': {
                    'EditForm': LookupFieldTemplate.SPFieldLookup_Edit,
                    'NewForm': LookupFieldTemplate.SPFieldLookup_Edit
                }
            };
            SPClientTemplates.TemplateManager.RegisterTemplateOverrides(lookupFieldContext);
        }

Any ideas ?

Regards

Cédrc