First and formost, the rulings in our religion are based on the Qur'an and on the hadith of the Prophet (saws). The discussion re: dogs takes place in the hadith, and not in the Qur'an or hadith qudsi, which is probably why you haven't found anything on it.
At the time of the Prophet (saws), dogs were kept to work, not as pets. A guide dog is a work dog, not a pet. Recently in my city, there was a big bruhaha about muslim cab drivers refusing to take guide dogs into their cabs. in the end, scholars said that they should allow them in. Here are some rulings that say it is permissible to accomidate guide dogs.
Can Guide-Dogs Enter the Mosque?
My Cousin Keeps a dog - can I pray in her house?
In conclusion, I strongly believe that the taxi driver would have been faithful to the teachings of Islam by accommodating the blind person with her dog rather than turning her away. The dog would have neither polluted nor rendered his vehicle impure, as the sacred precincts of the Prophet's mosque were not rendered impure by the frequent comings and goings of dogs as reported in the above traditions. If the dog had licked the cab driver's clothes or body during the course of the journey, it would have been necessary for him to simply wash them with anti-bacterial soap or a detergent before performing his ritual prayer. In other words, there would have been no need for him to perform any ritual cleansing of the vehicle itself. May Allah help us be true to the spirit of the Divine Laws, instead of fossilizing on their letter, amen.
I used to live with friends who had 4 dogs. I simply made sure my room was off limits to the dogs, and kept a clean set of clothes to pray in. It's not the ideal situation, but it's not the end of the world either.