Also it's worth noting the actual supply voltages... The European area (i.e. all CENELEC countries) have standardised on nominal 230/400V system at 50 Hz
UK, Malta, Cyprus: 240/415V 50Hz
ALL other countries 220/380V 50Hz
Appliences are now rated 230V Single phase or 400V 3-phase and work happily on either system. Actual supply voltages will gradually change to 230/400V.
Any equipment should be rated 230/400V 50hz and should have no problem dealing with either of the above supply voltages.
IT and Telecommunications equipment tends to be connected at 230V 50Hz i.e. between phase at 230V and ground referenced neutral at 0V.
I'm not sure about elsewhere but in Ireland where 3-phase power is used to provide 230V circuits each 230V circut must be protected by its own RCD and over current protection. Using 3-way 3-phase RCDs/Breakers that cover the whole system would not be an acceptable sollution on their own.
In general it would be rather unusual to plug an IT installation into a 3-phase socket. Typically you'd expect hardwired 230V 16A circuits all fed from a board of circuit breakers protected by RCDs etc.
In most countries 3-phase would only be used for loads that draw ?32A at 230V and in the UK & Ireland almost exclusively for industrial situations e.g. large motors.
UPS and various conditioning systems would also be quite normal in IT and Telecom systems
Most IT equipment is connected with normal domestic single phase plugs, usually CEE 7/7 except in the UK, Ireland, Cyprus, Malta (BS1363), Italy, Denmark and Switzerland.
Other common power connections in IT:
IEC 320 connectors are quite extensively used in IT, Telecoms and Studio setups too.