I don't think "old agreements" have been honored too well. A bridge from Russia to Crimea will cost millions.
http://www.ukraine-travel-advisor.com/images/BigMap-auto.jpg
Putin just spent $50 billion on the winter Olympics. What’s another billion fora nice bridge across the Kerch Strait. Looks like it was in the works anyway:
“Russia, Ukraine to construct bridge across Kerch Strait”