Welcome SMS for on-demand subscribers

Dear List, In the good old NITB days, it was possible to set up an "open" network where a foreign IMSI was able to register with the network, and at the first attempt the subscriber received sort of a "welcome" SMS with its random generated MSISDN. I found the on-demand option in the HLR, but I am not sure if the welcome SMS part is even possible since the network elements are now separated, no sign of it in any of the manuals though. I am working on a museum setup where there will be some pre-programmed SIMs in handsets, but it would be nice if the visitors themselves can use their own phone to connect and use the network. Worst case they can use the USSD command to get their MSISDN, but a welcome SMS would be nice to have. Regards, Csaba