When I was reading John Steinbeck's America and Americans, I came across the following sentence:
(1) An oil company may extend into transportation, or a food-processing firm invest its profits in magazines, but there is one thing the corporation cannot do. (p. 57)
Yes, the key for this kind of ellipsis to work is that there is parallelism (Subject+modal+verb + coordinating conjuntion + Subject+(modal)+verb). However, I wouldn't recommend using it at all.
Hi, Yasukotta and Gustavo—I agree with your analysis of the ellipsis, Gustavo, and with your recommendation that it not be used, at least by learners. This type of ellipsis is a species of the broader type of ellipsis known as Gapping.
Usually, Gapping does not involve ellipsis of a modal only. Steinbeck's sentence works gracefully, in my opinion, since the Gapping renders the second independent clause of a piece with the first, thereby assisting the "but"-clause.
In general, however, it is rather awkward simply to delete a modal from a second independent clause that shares the same modal as the first independent clause. The following examples don't sound very good to me:
(2) ? John will barbecue hamburgers for lunch and Sally make salads.
(3) ? John may fly to Paris and Sally take a boat to China.
(4) ? John should take tennis lessons or Sally learn to fly.
This is a type of ellipsis I "follow" in literature, and I have several specimens to share. One is another Steinbeck example, one involves a phrasal modal, and two have the Gapping of the modal in a coordinate subordinate clause.
(5) "In the morning we will sell the pearl, and then the evil will be gone, and only the good remain." (John Steinbeck, The Pearl)
(6) "In marriage, the man is supposed to provide for the support of the woman; the woman to make the home agreeable to the man." (Jane Austen, Northanger Abbey)
(7) "I've wished the houses would fall on me, or the stones sink under me." (Harriet Beecher Stowe, Uncle Tom's Cabin)
(8) "The uproar was appalling, perilous to the ear-drums; one feared there was too much sound for the room to hold—that the walls must give way or the ceiling crack." (Upton Sinclair, The Jungle)