I have gone through the Order Dated18 03 2015 and it is noted that Government has no authority to impose Life Tax once again on a vehicle which entered the state which was registered in another state. This is very clear from the Order. Since High Court expressed as above, the order is effective right from beginning and the RTA/RTO is not in order in imposing any life tax on the vehicles.
However, while concluding Honorable High Court mentioned as follows:
""...Direct the concerned respondent authority to hear and take note of specific power to impose life time tax on a vehicle which has been registered admittedly in another state. This exercise shall be completed within a period of three weeks from the date of communication of this order...."
The time is almost over and the authority concerned must have completed the exercise and whether they had come to a conclusion in the matter is not known.
However, I am of the view that quoting this Order sent attached to your query, a case can be filed and maintained in appropriate court. Therefore, you may contact a suitable Lawyer in the place where the cause of action arose and file a case in the appropriate court.
Once word of caution I wish to add here that although chances of winning are bright, it depends upon how the case is presented and how best the Order on the Write Petition is utilised as a case law.
Anyhow, all the best to you.