Most likely anything that does not jeapordize current safety rules at the ECTA, disqualify current bikes running with ECTA (where possible), or give unfair advantages to new entries over the records they are running on (again, where possible).... then those rules will be adapted.
"In general" though as far as your vehicle running at Maxton, if you can run it at the SCTA and it does not conflict with ECTA safety standards then it will be able to run at the ECTA.
The idea is that the ECTA is there to allow SCTA entrants to do their tune up runs and also qualify for records if possible, while at the same time (when possible) keeping the integrity of the existing ECTA records and the rules that were followed to obtain them.
Todd