It sounds like a great project and I wish you well, but, I don't want to sound grumpy, but can I make a plea? If you are going to publish a guide then please research it carefully, and if possible cross-check your information with cycling organisations in the countries concerned. And don't make vague and off-putting statements things like 'bike transport in trains in Spain is a disaster' which are extremely unhelpful (once your're actually in Spain trains can be a very practical proposition for travelling within a region - it's mainly long-distance journeys that are problematic). Otherwise don't do it: there's already enough incorrect or misleading information out there and you're not helping anyone if you add to it.
You can take bikes on pretty much all regional trains and all cercanías (if that's what you mean by local trains). There are some exceptions - the trains on the line going to Málaga airport used to be one but I've read that this has changed. Trains going into and out Madrid Atocha may also be problematic because of special security restrictions following the bombings there - however, as I say the position is one that changes so these restrictions may have been lifted.
You can also take bikes on the 'medium distance' services again with some exceptions (eg the Avant services).
Note that you need a ticket to take a bike on many newer trains - these tickets are free. If you are doing a journey with more than one leg (eg into Sevilla and then out again) you may need to get the ticket office staff to issue you with a ticket for each leg (the system doesn't seem to be able to cope with more complicated journeys).
You can't take bikes on long-distance services (ie the AVE services and other long-distance services) - this includes (officially at least) bikes in bags. I say officially, as I have got away with it - on one occasion after an argument with the train manager - an on the other couple of occasions I simply put the bike through the scanner and no one said a word. The only exception to this rule is if you book the whole cabin on a sleeper service.
As far as the buses/coaches are concerned, you need to distinguish between long-distance coach services where you definitely have to take the bike in a bag and the local commuter bus/coach services (ie those going into and out of the provincial capitals) where (I've been told) you might be able to ride with an unbagged bike bike but obviously only with the driver's agreement. The reason for the difference is that on the long-distance services the luggage compartment is full of luggage and the company won't want to risk damage to other passenger's luggage. On local services few if any the other passengers will have bags so this will be less of an issue - although the driver won't be happy if you hold the bus up.
There are a lot of companies running buses in Spain. So there may well be exceptions, and companies that leave it to the driver to decide, however i think that it's probably safest to assume that if you are travelling long-distance that you need to carry your bike in a bag.
I've carried my bike in a bag on the bus from Salamanca to Mérida (I forget which company runs this service but it is used by a lot of cyclists doing the Ruta de la Plata), I've no first hand experience of carrying a bike on a bus on a local service, but I've been told that (at least in the province of Granada) that you can do it if you ask nicely. I wouldn't rely on this, but if you're stuck and, for example, you need to get a bus into the nearest city to take a non-functioning bike to a bike shop then it would definitely be worth a try.
