No reason why there shouldnt be a daughter board in there as well. or an internal connector that lets them copy the roms. They might even have zif's - although I would expect soldered chips.
Main reason why it won't have one is simply cost, it's cheaper to produce a single board than a daughterboard/mainboard setup, the connector between them may only be a few pence but over the millions of ECU's Bosch make thats a lot of money. Same reason why there are no zif sockets involved not to mention the un-reliability aspect that may be added.
If they do use a main/daughter setup then logic implies that the mainboard is a re-usable component used in many ECU's but the daughter board would be more model specific but again based on cost this makes little sense as the same effective changes can be made with software on the mainboard not requiring the daughterboard, again pointing towards it being a single board setup.
If they do have a diagnostic socket or similar that the roms can be copied from how come it's such a big secret ? On an 8-9 year old ECU they surely would have been found by now and become common knowledge to avoid the big bills when losing keys ? In fact if this huge money saver was there surely we would be bombarded by every kid in the country who has the software to do it offering to do it cheaper than the next guy.....
Even at that only some of the Bosch ECU's used in alfas are readable (all are writeable, see Angel tuning link
) the split is roughly, petrol 147 = un-readable, diesel 147 = readable, exceptions 2.0 TS,GT, GTA = readable. So if the 147 in question is one of the un-readable ones it toally scuppers the idea of the ECU having been returned with the key data intact after major repairs/replacements. looking at pics here of Bosch ECU's from other cars (i am only familiar with BMW ones) and they all appear to be single board setups.
Doubt they are the sole company in the UK that know about them. Local Bosch specialist here doesn't know about them though that may not actually be saying much