Henle just came out with their edition of the second sonata. 

http://www.henleusa.com/en/detail/index.html?Title=Violoncello+Sonata+no.+2+F+major+op.+123_1280


Apparently the 3rd sonata wasn't published in Saint-Saens' lifetime and the last two movements have been lost. That's a shame. I quite like the 2nd.

http://www.prestoclassical.co.uk/w/287454