When I go Tmo online to order a free or $.99 Micro SIM for an older iPad, it makes you choose a data plan, shows the monthly plan cost ($20 or so) but doesn't charge you for the plan.
Try here: http://prepaid-phones.t-mobile.com/sim-card
No mention of a plan when I've ordered. Just the sims.
Also, I strongly feel, with all this attention to the free 200 data, TMo will soon stop or severely limit allowing unlimited access to it for anyone who can pop in a fresh Tmo SIM...
When you pop in a fresh sim you have to activate it; I bet they limit you to one sim per IMEI unless you talk to customer service and have a good story. Just guessing, haven't tried it.