Both Toyota and BP have adopted more responsible approaches than most of their industry brethren towards the environmental impacts of what they produce. That's why it's not terribly surprising to see them working together on a cleaner-energy project -- they both want to be out in front of the wave of change.
Toyota Motor Corp. has begun negotiations aimed at engaging in a joint research project with major oil company BP Plc., Nikkei Business has learned. The project concerns biofuels, alternative fuels derived from plant matter. [...] By entering into a new tie-up with BP, Toyota hopes to conduct research into matters such as the economic viability of biofuels, their effect on vehicles, and possible raw materials. Talks are currently focused on narrowing down the research interests. BP already operates a biofuel refinery in partnership with European companies, and is working to commercialize biofuels.
Academic debates about the viability of biofuels aside, if Toyota & BP together can't come up with ways to make biomass-based vehicle fuel work, I'd be convinced it's not a good prospect.
Cellulose ethanol made with enzymes is definitely something I'm keeping an eye on. The whole process of making ethanol could easily be made more efficient if only we tried.
I also suspect that there is so much corn ethanol being made because corn falls on some list of subsidized crop and "random fast growing weeds that don't need fertilizer" doesn't.