This module allow you to use 4b Pasat Internet with Ubercart.
I used uc_lacaixa as a base for the module, and it seems they would be similar.
Unfortunately, I needed to change most of the code.
It does not include MAC checking. I have not been able to make it work with php. Documentation is too poor and examples are really old.
It does include IP checking.
If you want custom receipts urls, you will need to make it yourself.
You may also want a custom payment page, but you are on your own too.
I needed to integrate this TPV with Ubercart and made this module. It seem to work, at least for me.
Of course you can use it with GPL v2 License, I will try, but I can't promise it will work or I will be able to correct any issue.
Probably, you will be in your own out there, but you already have a good point to start.