Will a T-Mobile SIM work in a locked iPhone 4?

I'm getting an iPhone 4 tomorrow which is locked to Orange. I have also been bought a T-Mobile SIM only contract. I was wondering if it is possible for a T-Mobile SIM to work on a locked Orange iPhone 4. I have checked other posts, and most people have tried it and say yes, but there's some uncertainty in my mind. Can I please have a certain answer?

Normally, no, but with the EE thing that they have going it may. Though I personally doubt it.

100% no, it will not work

I think it is not possible you need to get it unlock from network lock. Try inserting T-mobile sim card in Apple I-phone 4 if it's accept the sim and continue to work no problem. But if it won't accept the sim and displays invalid sim or asks for an unlock code. You need to unlock it to use other networ sim card like T-mobile. It's locked to which country orange network. If it is locked to Israel orange network, you can get remote unlocking service from the site http://www.mobile-unlocker.com/orange-israel-apple-iphone-unlocking-service/rs2wp10/ and unlock your Apple I-Phone 4 from the service provider lock. Then use with any GSM network sim card like T-mobile.