Can Nokia X,X+,XL run android apks? Can Nokia's new android phones run android apks just like in other androids via package installer? I heard there is no google play store, can I use a google play apk or flash gapps that brings one more question is their bootloader unlocked and rootable?
You can side-load any Android app provided you have the APK.

However, by default these phones do not come pre-installed with Google's core applications like the Play Store. But you can "hack" the devices and install Google Apps. Needless to say it will void warranty and root access is required.

There is this guide in XDA Forums that should help people install Google Services on their Nokia X device.