RE: Burgos

Yes... there is accommodation in both these places. I understand there was a very nice new albergue that opened in Rabe de las Calzadas last year. We walked only as far as Rabe from Burgos, instead of having a rest day in Burgos itself, and it felt like a rest day!
Here is a thread that talks about the new albergue in Rabe: http://www.caminodesantiago.me/board/el-camino-frances/topic6962.html?hilit=rabe

Margaret

It will take you longer than 3 days to walk from Burgos to Sarria. I saw your post on the Rabe thread about shuttle buses. There aren't "shuttle buses" like you're thinking; they are regular buses that everyone uses that go from town to town. Not all towns on the Camino are served by buses though. You can get the bus schedules from the Tourist Information offices & sometimes in the albergues. There are different companies, some running the same routes, & the information changes from time to time, but the Tourist Offices should have the most up-to-date information.

Kelly