When you say "3G" I presume you mean access to the internet via 3G/carrier data?
Not possible I'm afraid - 48 don't support data roaming abroad.
You are restricted to wifi where available unfortunately.
If you need data then you might be better off picking up a cheap local SIM with a data package.
Dual SIM phones are useful in this context so you can have your local foreign SIM and 48 Irish SIM active at the same time.
Hope this helps.
