When configuring the Netatmo weather station on a firewalled network, the app tells you : "Sorry, Enterprise network are not supported, blah blah blah, send an email to the support, blah blah blah".
This is (of course) just a joke !
You just have to NAT TCP port 25050 to let Netatmo weather station reach its server (188.8.131.52 for me).
By the way, this is a very good (french) product and there is an API : http://dev.netatmo.com. Youpi, I can easily display inside temperature and CO2 level on screens in my office. Colleagues cannot offer apologies anymore for not airing their room !