Not sure which direction the switch is headed, but I can tell you the system will function on either 110v or 220v systems.
Dial tone is not a real issue, as the system will connect the set to the selected line whether dialtone is present or not. What may perplex the system is the difference in ring cadence/voltage on inbound calls.
On an ACS, if you dial feature 59, it will display the firmware version of the switch and the country code (for US it will say P ACS R3.0.3 C01, where COuntry code 1 is US). There is no way short of an IC change to alter the country code that I know of.
While bringing in a switch from Europe to the US shouldn't cause grief, understand that some US features and functions may actually be illegal in Europe. One that comes to mind is music on hold. Strict prohibitions against playing other than "jewelry box" MIDI style computer generated music for callers on hold could result in liability should one install a radio or such as a MOH source in many European countries. Be aware, and good luck.