The case is different for different industry. Consider FMCG and consumer durables. In case of FMCG the relationship between the consumer and the brand ends as soon as it is purchased. A consumer durable where the consumer may have to go back to the company for after sales service.In case of service industry it will be totally different.
Coca Cola tried to kill the brand Thums Up after buying it from Parle. However the brand pull was so strong that people asked for a Thums Up rather than a Coke. After many years of relegating the brand spend, Coca Cola had to relent. Thums Up is the largest cola brand, Pepsi comes second and Coca Cola.....sometimes it sells.
Take the case of Kissan Ketchup. Kissan was taken over by Hindustan Lever (now HUL) and they understood that people used to ask for 'Kissan' not just ketchup. So the kept the brand and promoted the same.
Some other strong brands were however killed. E.g. Mangola, the best mango based drink brand ever. Now they got Maaza into the game. However I still hear people asking for Mangola.
Ofcourse Tatas won. Its a win win situation for Tatas.
Their strategy was to take design and engineering inputs from Jaguar and slowly incorporate it in their other offerings. To develop such engineering capabilities would have taken a decade for Tatas. They got it at one go.
Secondly they were present in CV and Passenger cars/SUVs. However to have a marquee brand in the portfolio adds weight to the name. Thirdly they got access to more car markets than they would have with their own Tata brand. They got to learn about those markets through Jaguar, which otherwise would have taken lots of money and time on their part.
With this basic three pronged benefit, they got all factors of the marketing mix correct. Hence Tatas win hands down with Jauguar deal and also keeping the same brand name.
because consumers acquired an idea before buying this product and they became believer, now if you want to change the brand's name, you should think about the consumer behavior and attitude towards the new brand,