SpacePhone utilises national testing prefixes if available in the country, otherwise we'll resort to a prefix that is not globally routable. This means your phone numbers are not reachable over public PSTN networks, but also that the prefix will not collide with existing services.
Reference documents for per-country laws and regulations:
+31, The Netherlands, Nummerplan telefoon- en ISDN-diensten
+44, United Kingdom, Telecoms numbering
+49, Germany, Nummerierungskonzept
There are not many restrictions as to how you implement SpacePhone in your hacker space, hence should in most points below.
Your hacker space: