As to necessity of regulation
Good point raised there, as to whether regulation is justified at all here.
Again one should look at different cases separately. Basically, F2M termination implies that (mostly) regulated fixed line incumbents are forced to accept MNOs demands for termination charges, and set retail prices as termination charge plus regulated margin. They cannot threaten to disconnect or set retail prices so high that customers don't make F2M calls, nor can they counter with high M2F prices as bargaining threat or punitive measure. In other words, there is not enough "countervailing bargaining power", as has also been found in a few court cases, and MNOs can set their F2M charges at will. That is, MNO can set F2M charges at will and cash in.
To worsen things, in some countries fixed line callers can't distinguish which mobile network they are calling, which means that consumers effectively face the average price over different mobile networks -- and mobile networks have even stronger incentives to set higher prices.
So far so good, but what happens to this money? Part or all of it (this is a point of contention) will handed over to mobile customers -- the waterbed effect mentioned above. Thus we have a transfer, total or partial, of money from fixed-line users to
Thus it has been concluded that there are clear market failures, partly caused by existing regulation on fixed networks, for sure, that need repairing. So either cut regulation on fixed networks (for which competition may still be lacking -- but then again Reding's whole exercise is about having fixed and mobile networks compete!) or impose regulation on mobile ones -- your choice.
As concerns M2M charges, the case is much less clear-cut. Economic theory has for the last 10 years produced many contradicting results, on whether firms would agree on low or high termination charges if they talk to each other in the absence of regulation. The answer is "depends". A sufficiently clear case can still be made with respect to asymmetries: It has become clear that high M2M charges, in particular if they are symmetric, make small networks pay significant amounts of money to larger networks, which certainly doesn't help them in the entry phase at least. (It's not true that in- and outgoing payments always cancel out).
As concerning "Brussels" -- I feel a kind of Brussels-meddling-in-our-affairs kind of mood here. If "Brussels" didn't exist, national governments would do most of the same things on their own, and they actually did. Furthermore, at least in telecoms, "Brussels" has for a long time copied quite faithfully what happened in the UK (or let's say, since the UK has a big say in "Brussels", the latter quite often adopted as official policy what had been thought up in the UK before. Thus "Brussels bashing" turns out to be a sort of auto-flagellation). The latest "Brussels attack" on termination charges is the logical continuation of this policy, and not some kind of continental conspiration. (this doesn' mean all their ideas are good, hey!)