Yes! In that case you should write to the organising team well in advance. We will put you in contact with the local bikekitchens or ask the projects we will visit for a bike for you. If you have the time to arrive early enough, there are some in most big cities where you can try to build a bike cheaply or for a donation. In the past some participants have built their own bicycle out of recycled parts and gave them away at the end of the tour.
On previous years some people bought cheap-crappy bikes and later the group had to help them out a lot. A used bike is in most cases better than a new one.
It is also possible to share one bicylce between two or more persons along the route: Maybe someone takes the tour from point A to B, so that you could arrange to take over the bike from point B to C. For that you should register and write to the mailing-list you will be added to.