Can I scan data from a paper for my own research? I am a PhD student working in mechanical properties of materials and will be finishing soon. My PhD is in numerical modelling, so I need experimental data (stress-strain curves) to validate my programs. And this is where the situation starts to tangle:


There is a set of data published by a group from another university that I would like to test in my model. This data comes from lab experiments and they also did some numerical modelling trying to replicate it.
Some data is published in a paper and some other is published in a PhD thesis.
The PhD thesis is not available online, but can be accessed publicly (physically) in the library of the other university.
I have asked for the raw data and a copy of the PhD thesis to the other group and the response I got was: we are not going to send it to you, and we prohibit you to use any of our data in your research.
I then learned that there is a bad relationship between our group and their group because of historical competition.


Furthermore:


I have scanned the data in the paper (I created a program to fit the curves in the image and get an analytical expression for it) and run my simulations.
I happen to have a copy of the thesis (a third person gave me a scanned copy), so I did the same.
In both cases my numerical results are significantly better than those from the other group, which is why we think that my research would have a high impact.
Since I scanned their data I can generate my own figures, so I guess image copyright is left out of the equation.
I will, of course, cite where the data comes from.


I believe in open science, so I would never do what they did. However, I get their point on not wanting me to have the data, since they did the experiments. What I believe is not ethical/appropriate is banning me from using any of their data sets. 

Finally, we could prepare these experiments in our lab, but it will take a couple of years, resources and expertise (which I don't have), so this is not viable.

So my questions are:


What are the implications of publishing my comparison with their data?
Is it ethical, given that I have been denied the use of the data?
Would there be any additional problems if we decided to publish a paper or publish the thesis as a book?
It might be helpful to consult some legal assistant at your university, because there is a bad relationship between our group and their group, so if they are really determined, they might want to make problems, so it would be good to have a backup plan, or just be sure that you are really not breaking any laws, and that your party will stand by your side in case things from the other group's side become dirty. (This is an awful situation, though.)

But that aside, the line of reasoning is quite straightforward: anything one publishes becomes publicly available and viable for research by others. I understand that they didn't publish a table with numerical data, but if you think that recreating it from a plot is methodologically fine, then in your paper you should just describe the method and of course give credit to the source.