Commuter service around Budapest: The BHEV
The BHEV is today a department of the "Budapest Transport Company", a huge company operating all of Budapest's buses, trams, trolley-buses, metros, the cogwheel railway and even - as far as I know - the Castle Funiculare.
The four lines are not connected to each others, the last connection between the Rackeve line and the Csepel line was abandoned in the '80s. The transfer of trainsets or stock happens using the MAV connections.
The BHEV (in common use: HEV) clearly differs from the tram net: it uses 1000V DC, while the trams in Budapest uses 600V DC. (The abandoned Budafok net had a long common part with the tram on the Fehervari street. They used of course 600V DC without any conversion. The HEV trains were extremly slow using the half voltage. The conductor switched over the lights at the end of the common line.) The HEV has with the exception of a very short piece in Csepel Main Street, separated rails and runs faster (appr. 70km/h) than the trams. All lines use the EMUs described in my version on "hunpriv". The old ones (M IX) are used on the Csepel line.
The BHEV is practically fully electrified. (perhaps not all industry connections). The last 15km of the Rackeve line was electrified in the '70s, earlier there were Diesels there, mainly similar types as the MAV M44 and M31.
The HEV has several connections with the MAV and serves several industry sites. It has a not very big freight car stock too. The "locomotives" are very different: most of them are similar to the LAG Bo electric unit (I think from Trix HO model, or ROWA earlier), a steel inforced short wooden box with windows on the front, two large doors (as the box is almost empty inside) and a single pantograph in the center. There are however two more locomotive-like units (the above mentioned "V43"s observed on the Godollo line) and several Bo'Bo' units which were earlier passanger railcars - now the seats removed. I think for serving some industry connections there are Diesels still available.
The HEV runs very reliable and punctual. On the Szentendre line between Budapest and Bekasmegyer (a big housing estate at the border of Budapest) they start in the rush hours in every 5 minutes. (It is a small disaster if they fail: there is no other possibility there to transport 6000 people in an hour!)