I used support's sample program RangeBarsMinMaxIndicator2.java mentioned in thread viewtopic.php?f=65&t=44000&p=57676&hilit=range+bar#p57676 .
I tested it with 15 pips range bars and pricerange = 5 and the output was the following

2012-04-01 10:58:02 StartTime: 2012-03-25 21:00:00.0 EndTime: 2012-03-25 22:15:00.0 O: 1.32705 C: 1.32803 H: 1.32803 L: 1.32643 V: 4254.975 FEC: 6
2012-04-01 10:58:02 StartTime: 2012-03-23 15:30:00.0 EndTime: 2012-03-25 20:45:00.0 O: 1.3262 C: 1.32684 H: 1.32717 L: 1.32568 V: 109800.17 FEC: 214
2012-04-01 10:58:02 StartTime: 2012-03-23 14:30:00.0 EndTime: 2012-03-23 15:15:00.0 O: 1.32798 C: 1.32673 H: 1.32833 L: 1.32673 V: 45078.74 FEC: 4
2012-04-01 10:58:02 StartTime: 2012-03-23 14:15:00.4 EndTime: 2012-03-23 14:15:00.5 O: 1.32525 C: 1.32685 H: 1.32685 L: 1.32525 V: 0.0 FEC: 0
2012-04-01 10:58:02 StartTime: 2012-03-23 14:15:00.2 EndTime: 2012-03-23 14:15:00.3 O: 1.32365 C: 1.32525 H: 1.32525 L: 1.32365 V: 0.0 FEC: 0

Why is the StartTime and EndTime exactly on a quarter of an hour?
This looks like a bug. If you take 10 pips range bars it looks ok.
Please correct this asap.

Bug approved with JForex DEMO version
Dukascopy ver. 2.15
JForex API ver. 2.6.63

Range bars are being generated from ticks. However, it's almost impossible to generate range bars with bigger price range value from ticks due to there are too much of them.
The system will operate too slow.
So, for bigger price ranges we take candles, split them into ticks and generate range bars.

For 15 pips range bars, we take 1 hour candles. The procedure of range bars generation from candles is as follows:
We take target candle and split it into 4 ticks with four prices (open, high, low, close) and with 0.25 of candle's volume each.
Thus we will get 4 ticks (for one hour candle with time let's say 13:00 ) with times 13:00, 13:15, 13:30 and 13:45. Those ticks we will use to create range bars.

Due to those ticks have not real times (13:00, 13:15, 13:30 and 13:40) range bars have them too.
Note, that this algorithm is used only for history generation, in-progress range bars are being generated from real ticks.

1) This is also the reason why indicator functions get imprecise in the History Tester, isn't it?

2) From what range bar size do you start this process?

1) Yes it is, but only for those price ranges, which history is generated from candles.
2) Now we use the next method to get a suitable period for the passed pips count:

public static Period getSuitablePeriod(int pipsCount) { 
    if (pipsCount <= 2) { 
        return Period.TICK; 
    } 
    else if (pipsCount <= 10) { 
        return Period.ONE_MIN; 
    } 
    else { 
        return Period.ONE_HOUR; 
    } 
}