Indian bikes, like many Indian products would find great success in Pakistan, because in the end, the consumer wants value. A common man will compare the sophistication of a product with the amount of money he/she is capable and willing to spend on it. To the end user, it is often irrelevant where a product is from. Brand recognition is based on quality and if the Indian bikes meet the performance parameters and do so at an affordable price, you can bet people will buy them.
The problem is that investing in a new nation, even one largely similar to the domestic market, requires massive outlays of capital. It is one thing for a western company to be reluctant to invest in Pakistan, due to the constantly fluctuating economy and lack of enforced regulations that breed corruption...for an Indian company the risks are even greater. What happens if there is another conflict? What if they are kicked out and their assets become Pakistani or Indians demand the curtailment of business in Pakistan and it starts to adversely affect the brand?
So, while it makes a great amount of sense and I am huge supporter of cross border communication and cooperation...the risks faced by companies from both sides face is still huge and may not be justifiable to its' stake holders.