They capture one *field* every 1/50th of a second, and interlace it.
The reason for this is that it was hard to scan a full 625 lines in 1/50th of a second, and it would have required ludicrous bandwidth for the AM transmitters of the day and massive output valves to drive the scan coils in TV sets which would then produced huge flyback spikes.
So the decision was to scan 312.5 lines per field, offset slightly, with each pair of fields forming one 1/25th of a second frame. Telecine was easy in the UK because you could speed the film up a little and then each TV frame would be two fields per film frame.
If you shoot 50i you can deinterlace to 25p by combining the two sets of scan lines from each field with a bit of clever processing to hide the "combing" caused by things moving between fields, or you can double it up to 50p by just copying each line out twice with a bit of clever processing to smooth out the steps. I could post some video clips showing this if you were interested.
Of course modern digital TV cameras are capable of shooting 60p as you say, but anyone shooting "telenovela" stuff is going to be shooting 60i.