Yes, although depends on coverage of the mobile network.
Telkomsel and Indosat would have the best coverage.
My phone didn't work when I got to jakarta, it was with Indostat.
i have used a simpati sim in lombok, it worked fine.
It will work but you will find you use a lot more credit as it is 'roaming' when you are in Java.. so if it is just for emergencies, it shouldn't really be a problem.
You can buy a prepaid SIM card and then subscribe for Blackberry Internet Service here so you can continue receiving emails using Blackberry service from local operator. Just buy a Simpati prepaid card, activate the SIM card and follow these steps:
1. Activate the GPRS service by texting "GPRS" (without the quotes) to 6616. You will receive the following notification: "Your request for GPRS setup already received. Please wait max 48 hours for successful activation.” And then you will receive this message “Welcome to Telkomsel GPRS Service! Your service has been activated. Please visit www.telkomsel.com for more information.” Your GPRS service is now active.
2. Register for Blackberry Internet Service. For weekly subscription, type "bbminggu reg" (without the quotes) to 333. For daily subscription, type "bbhari reg" to 333. Daily subscription is only IDR 5,000/day and weekly subscription is only IDR 35,000/week.
3. You will receive a following SMS for confirmation (it's in Bahasa Indonesia):
“Anda akan dikenakan biaya berlangganan BlackBerry Internet Service Rp 180ribu/30 hari utk akses tanpa batas (biaya tdk termasuk streaming, roaming internasional & penggunaan BlackBerry sbg modem).Jika SETUJU, ketik BB<spasi>ON & kirim ke 333.Pastikan Handset anda support layanan BlackBerry”.
4. Just text "BB ON" and send it to 333. If the process is successful, you will receive a confirmation SMS. Pull your battery to restart, and your Blackberry is now operating fully, no expensive roaming cost :)
5. To unsubscribe the BIS, text "BB unreg" to 333.Edited: 25 April 2010, 14:54
And if you just want to make phone calls, just put the SIM in and make calls. You can top up your credit at little shops and stalls all over the place. And if you need to dial overseas on a SIMPATI/Telkomsel card, put 01017 in front of the country code/phone number (wthout the zero) . Much cheaper. I think Xcel and Indosat use 01016. But as a poster above wrote, SIMPATI/Telkomsel are reputed to have the best coverage. IT's odd that the poster above had problems in Jakarta. An Indonesian card bought anywere is not 'roaming' there- it's still in Indonesia. Maybe you needed credit...Edited: 25 April 2010, 20:15
Thanks for all the great info!