Several Electrical Mains into a Single Panel
First, you can have only one meter/service per occupancy (unless you have something really weird).  An occupancy is a single tenant, within reason.  For instance a single family home gets one service.  If that house is later subdivided into four apartments, it could have four meters and four services, but the power company will be reluctant to provision all this, so they will insist on proof that the city authorized the subdivision.

Similarly, a large building subdivided into live-work spaces, workshops, studios or retail stores may  be able to get a separate utility meter and service for each tenancy.  

Alternately, the landlord can take one service, and fit his own "submeters" and then rebill the tenants.  

So what happens when the 4-unit apartments are turned back into a single family home? Awkward.  The power company may be able to bill them on one bill. Electrically, you have to live with it, and keep each service's hots, neutrals and grounds separate.  If you've got four 60A services and want to fit a heat pump with a 70A aux heat, you've got a problem.  



You can't feed one main panel from two meters.  (unless the power company specifically wires you up that way, and remember, the point of demarcation isn't the meter, it's below the meter, and in that case, it would be on them).  This would be paralleling without using equipment made for paralleling, and would raise huge issues for overcurrent protection, maintenance shut-off, and finding main panels able to support merging main feeds (you won't).  And if any of the services are out of phase with each other -- KABOOM! That last is why even if you were do this harebrained idea, you'd want overcurrent protection before the merge. 

What you can do is install one new, proper main service (e.g. 200A) with one main panel.  Then later at your leisure, cut over each old panel to be a subpanel of the new main.  If you are in Europe, the new main could be 3-phase and serve a single phase to each subpanel.  So for instance, in that case, you'd provision your heat pump's 70A aux heat directly off the new main, bypassing the subpanels altogether.  You could cut loads over to the new main at your leisure, and eventually deprecate the old panels.  But -- 

Just to sanity check here, are you sure the building's best value isn't subdivided?  If so, take care to arrange things so a rollback is possible.  If so, the plan might be leave the subpanels intact, and go with submetering if that day ever comes.